Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome

Clinical Outcome of Monochorionic Diamniotic Twins with Intrauterine Growth Restriction

OBJECTIVE

 This study investigated the clinical outcome of monochorionic diamniotic (MCDA) twins with selective intrauterine growth restriction (sIUGR).

STUDY DESIGN

 International Peace Maternal and Child Health Hospital of Shanghai ultrasound database was investigated to identify all MCDA delivered from January 2013 to December 2017. After identifying 43 pairs of MCDA twins with sIUGR and 282 pairs of normal MCDA twins, we compared clinical outcomes between the two groups.

RESULTS

 Compared with normal twins, sIUGR fetuses had significantly shorter gestational age at delivery, smaller average birth weight of both twins, more significant intertwin difference in birth weight, lower Apgar scores, and higher intrauterine fetal demise (IUFD) rate, and smaller placental weight. The rate of abnormal umbilical cord insertions and abnormal blood flow in the ductus venosus (DV) and middle cerebral artery (MCA) is significantly higher in the sIUGR group. In addition, the subtype analysis of sIUGR groups indicated the poorest outcomes in type II with no significant difference between type I and III.

CONCLUSION

 MCDA twins with sIUGR generally exhibited limited clinical outcomes than normal MCDA twins. These limitations are mainly associated with abnormal umbilical cord insertions and blood flow in the DV and MCA. Clinical outcomes differed among the three types of sIUGR, with type II having the worst prognosis and the highest IUFD rate.

KEY POINTS

· sIUGR generally exhibited limited clinical outcomes than normal MCDA twins.. · These limitations are mainly associated with blood flow of the DV and MCA.. · sIUGR with type II has the worst prognosis and the highest IUFD rate..

Placental architectural characteristics following laser ablation within monochorionic twins complicated by twin-twin transfusion syndrome: A systematic review and meta-analysis of outcomes

INTRODUCTION

Twin-twin transfusion syndrome (TTTS) complicates approximately 10%-15% of all monochorionic twin pregnancies. The aim of this review was to evaluate the placental architectural characteristics within TTTS twins following laser and elucidate their impact on fetal outcomes and operative success.

MATERIAL AND METHODS

Five databases were searched from inception to August 2023. Studies detailing post-delivery placental analysis within TTTS twins post-laser were included. Studies were categorized into two main groups: (1) residual anastomoses following laser and (2) abnormal cord insertion: either velamentous and/or marginal or proximate. The primary outcome was to determine the proportion of TTTS placentas with residual anastomoses and abnormal cord insertions post-laser. Secondary outcomes included assessing residual anastomoses on post-laser fetal outcomes and assessing the relationship between abnormal cord insertion and TTTS development. Study bias was critiqued using the Joanna Briggs Institute checklists and Cochrane risk of bias tool. Random-effects meta-analysis was used, and results were reported as pooled proportions or odds ratio (OR) with 95% confidence interval (CI). PROSPERO registration: CRD42023476875.

RESULTS

Twenty-six studies, comprising 4013 monochorionic twins, were included for analysis. The proportion of TTTS placentas with residual anastomoses following laser was 24% (95% CI, 0.12-0.41), with a mean and standard deviation of 4.03 ± 2.95 anastomoses per placenta. Post-laser residual anastomoses were significantly associated with intrauterine fetal death (OR, 2.38 [95% CI, 1.33-4.26]), neonatal death (OR, 3.37 [95% CI, 1.65-6.88]), recurrent TTTS (OR, 24.33 [95% CI, 6.64-89.12]), and twin anemia polycythemia sequence (OR, 13.54 [95% CI, 6.36-28.85]). Combined abnormal cord (velamentous and marginal), velamentous cord, and marginal cord insertions within one or both twins following laser were reported at rates of 49% (95% CI, 0.39-0.59), 27% (95% CI, 0.18-0.38), and 28% (95% CI, 0.21-0.36), respectively. Combined, velamentous and marginal cord insertions were not significantly associated with TTTS twins requiring laser (p = 0.72, p = 0.38, and p = 0.71, respectively) versus non-TTTS monochorionic twins.

CONCLUSIONS

To the best of our knowledge, this is the first review to conjointly explore outcomes of residual anastomoses and abnormal cord insertions within TTTS twins following laser. A large prospective study is necessitated to assess the relationship between abnormal cord insertion and residual anastomoses development post-laser.

Atypical twin-to-twin transfusion syndrome case managed in a single centre in Indonesia with fetoscopic laser photocoagulation and amniopatch: 'Case Report'

Introduction and importance

The diagnostic criteria for Quintero staging in twin-to-twin transfusion syndrome (TTTS) are not applicable in all cases of TTTS, such as those in which the symptoms overlap with other monochorionic twin complications such as selective intrauterine growth restriction (sIUGR).

Case presentation

A 25-year-old woman, G1P0A0, at 22-24 weeks' gestational age was diagnosed with TTTS, with no outstanding history of medication use during pregnancy, and no family history of genetic disorder or twin pregnancy. In the donor twin, persistently absent end-diastolic flow in the umbilical artery was observed using Doppler velocimetry. Polyhydramnios was observed in the recipient twins. The fetal weight discordance between the twins was 39%. After 2 weeks of follow-up, the authors performed fetoscopic laser photocoagulation and successfully ablated five vascular anastomoses and amnioreduction by 2.5 l. Five days after the laser surgery, the patient developed amniotic fluid leakage, and an amniopatch was performed. The authors did the caesarean section at 34 weeks because of severe preeclampsia, the donor and recipient birth weights were 1,120 g and 1,837 g, respectively (weight discordance 39%). The APGAR scores were 3/4 and 6/8, respectively. The donor twin died 6 days after delivery due to respiratory failure, and the recipient twin survived. Neonatal echocardiography of the surviving twin showed no tricuspid regurgitation. No long-term follow-up was performed.

Clinical discussion

The traditional diagnostic criteria for TTTS stage 3 were not met and overlapped with the diagnostic criteria for sIUGR type 2. This is the first procedure reported in Indonesia for atypical TTTS with the outcome, one twin survived.

Conclusion

Some TTTS cases do not meet traditional diagnostic criteria and overlap with other monochorionic twin complications.

Pregnancy and obstetric outcomes of dichorionic triamniotic triplet pregnancies with selective foetal reduction after assisted reproductive technology

BACKGROUND

It is generally beneficial and recommended that dichorionic triamniotic (DCTA) triplet pregnancies be reduced to monochorionic (MC) twin or singleton pregnancies after assisted reproductive technology (ART). However, some infertile couples still have a firm desire to retain twins. For this reason, the best foetal reduction strategies need to be available for infertile couples and clinicians. Given that data on the elective reduction of DCTA triplet pregnancies to twin pregnancies are scarce, we investigated the outcomes of elective reduction of DCTA triplet pregnancies through the retrospective analysis of previous data.

METHOD

Patients with DCTA triplet pregnancies who underwent elective foetal reduction between January 2012 and June 2020 were recruited. A total of 67 eligible patients with DCTA triplet pregnancies were divided into two groups: a DCTA-to-dichorionic diamniotic (DCDA) twin group (n = 38) and a DCTA-to-monochorionic diamniotic (MCDA) twin group (n = 29); the basic clinical data of the two groups were collected for comparison.

RESULTS

Compared with the DCDA-to-MCDA twin group, the DCTA-to-DCDA twin group had lower rates of complete miscarriage (7.89% versus 31.03%, p = 0.014), early complete miscarriage (5.26% versus 24.14%, p = 0.034), late preterm birth (25.71% versus 65.00%, p = 0.009) and very low birth weight (0 versus 11.11%, p = 0.025). In addition, the DCTA-to-DCDA twin group had higher rates of full-term delivery (65.71% versus 25.00%, p = 0.005), survival (92.11% versus 68.97%, p = 0.023), and taking the babies home (92.11% versus 68.97%, p = 0.023) than did the DCTA-to-MCDA twin group. In terms of neonatal outcomes, a significantly greater gestational age (38.06 ± 2.39 versus 36.28 ± 2.30, p = 0.009), average birth weight (3020.77 ± 497.33 versus 2401.39 ± 570.48, p < 0.001), weight of twins (2746.47 ± 339.64 versus 2251.56 ± 391.26, p < 0.001), weight of the larger neonate (2832.94 ± 320.58 versus 2376.25 ± 349.95, p < 0.001) and weight of the smaller neonate (2660.00 ± 345.34 versus 2126.88 ± 400.93, p < 0.001) was observed in the DCTA-to-DCDA twin group compared to the DCTA-to-MCDA twin group.

CONCLUSION

The DCTA-to-DCDA twin group had better pregnancy and neonatal outcomes than the DCTA-to-MCDA twin group. This reduction approach may be beneficial for patients with dichorionic triamniotic triplet pregnancies who have a strong desire to have DCDA twins.

Outcome of monochorionic diamniotic twin pregnancy with selective intrauterine growth restriction, a single center study in China

INTRODUCTION

This retrospective study aimed to evaluate clinical outcomes of monochorionic diamniotic (MCDA) twins with selective intrauterine growth restriction (sIUGR).

MATERIALS AND METHODS

MCDA twins, either sIUGR and non-sIUGR, underwent expectant management from 2016 to 2019 in our hospital were included. sIUGR fetuses were classified into three types according to umbilical artery Doppler assessment. Non-sIUGR were considered as the control group. Outcomes were pregnancy outcomes and maternal complications.

RESULTS

Forty-three sIUGR (type I: 23; type II: 14, and type III: 6) and 282 non-sIUGR fetuses were included. The sIUGR group had a significantly earlier birth, lower birth weight of the twins, larger inter-twin weight difference, lower Apgar score of the twins, and higher intrauterine fetal death (IUFD) than the non-sIUGR group (all p < 0.001). The same trend was found in the sIUGR type II group compared to type I and III groups. A significantly lower gestational diabetes rate (p = 0.01) and placenta weight (p < 0.001), and higher proportions of abnormal placental umbilical cord insertion (p < 0.001), and ultrasound Doppler monitoring indicators (p = 0.006) were found in the sIUGR group than the non-sIUGR group.

CONCLUSIONS

The MCDA twins with sIUGR showed poorer outcomes than the non-sIUGR group. Doppler interrogation was a useful clinical marker for fetal outcome.

Selective fetal growth restriction in dichorionic diamniotic twin pregnancy: systematic review and meta-analysis of pregnancy and perinatal outcomes

OBJECTIVE

Most of the published literature on selective fetal growth restriction (sFGR) has focused on monochorionic twin pregnancies. The aim of this systematic review was to report on the outcome of dichorionic diamniotic (DCDA) twin pregnancies complicated by sFGR.

METHODS

MEDLINE, EMBASE and The Cochrane Library databases were searched. The inclusion criteria were DCDA twin pregnancies complicated by sFGR. The outcomes explored were intrauterine death (IUD), neonatal death and perinatal death (PND), survival of at least one and both twins, preterm birth (PTB) (either spontaneous or iatrogenic) prior to 37, 34, 32 and 28 weeks' gestation, pre-eclampsia (PE) or gestational hypertension, neurological, respiratory and infectious morbidity, Apgar score < 7 at 5 min, necrotizing enterocolitis, retinopathy of prematurity and admission to the neonatal intensive care unit (NICU). A composite outcome of neonatal morbidity, defined as the occurrence of respiratory, neurological or infectious morbidity, was also evaluated. Random-effects meta-analysis was used to analyze the data, and results are reported as pooled proportion or odds ratio (OR) with 95% CI.

RESULTS

Thirteen studies reporting on 1339 pregnancies with sFGR and 6316 pregnancies without sFGR were included. IUD occurred in 2.6% (95% CI, 1.1-4.7%) of fetuses from DCDA pregnancies with sFGR and 0.6% (95% CI, 0.3-9.7%) of those from DCDA pregnancies without sFGR, while the respective values for PND were 5.2% (95% CI, 3.5-7.3%) and 1.7% (95% CI, 0.1-5.7%). Spontaneous or iatrogenic PTB before 37 weeks complicated 84.1% (95% CI, 55.6-99.2%) of pregnancies with sFGR and 69.1% (95% CI, 45.4-88.4%) of those without sFGR. The respective values for PTB before 34, 32 and 28 weeks were 18.4% (95% CI, 4.4-38.9%), 13.0% (95% CI, 9.5-17.1%) and 1.5% (95% CI, 0.6-2.3%) in pregnancies with sFGR and 10.2% (95% CI, 3.1-20.7%), 7.8% (95% CI, 6.8-9.0%) and 1.8% (95% CI, 1.3-2.4%) in those without sFGR. PE or gestational hypertension complicated 19.9% (95% CI, 12.4-28.6%) of pregnancies with sFGR and 12.8% (95% CI, 10.4-15.4%) of those without sFGR. Composite morbidity occurred in 28.2% (95% CI, 7.8-55.1%) of fetuses from pregnancies with sFGR and 13.9% (95% CI, 6.5-23.5%) of those from pregnancies without sFGR. When stratified according to the sFGR status within a twin pair, composite morbidity occurred in 39.0% (95% CI, 11.1-71.5%) of growth-restricted fetuses and 29.9% (95% CI, 3.5-65.0%) of appropriately grown fetuses (OR, 1.9 (95% CI, 1.7-3.1)), while the respective values for PND were 3.0% (95% CI, 1.8-4.5%) and 1.6% (95% CI, 0.9-2.6%) (OR, 2.1 (95% CI, 1.0-4.1)). On risk analysis, DCDA pregnancies complicated by sFGR had a significantly higher risk of IUD (OR, 5.2 (95% CI, 3.2-8.6)) and composite morbidity or admission to the NICU (OR, 3.2 (95% CI, 1.9-5.6)) compared to those without sFGR, while there was no difference in the risk of PTB before 34 weeks (P = 0.220) or PE/gestational hypertension (P = 0.210).

CONCLUSIONS

DCDA twin pregnancies complicated by sFGR are at high risk of perinatal morbidity and mortality. The findings of this systematic review are relevant for counseling and management of complicated DCDA twin pregnancies, in which twin-specific, rather than singleton, outcome data should be used. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Artery-to-vein anastomoses in unequally divided placentas and their association with birthweight discordance

INTRODUCTION

This study investigated the impact of the shared intertwin circulation in unequally divided monochorionic (MC) placentas on fetal growth.

METHODS

This retrospective analysis included color-dyed, unequally shared placentas from two tertiary centers. Exclusions included twin-twin transfusion syndrome, twin anemia polycythemia sequence, and lethal anomalies. Measurement of the external diameters and areas of the artery-to-artery (AA), artery-to-vein (AV), and vein-to-vein (VV) anastomoses was performed. The ratio of the shared circulation (AV ratio) was determined by comparing the areas of the summed venous components of shared AV anastomoses to those in the individual AV anastomoses of the smaller placental part. The birth weight ratio/placental ratio (BWR/PR), total AV size areas and net AV transfusion were calculated. Univariable and multivariable linear regressions were performed to assess the relationship between BWR/PR, the AV ratio, the areas of the different anastomoses and cord insertion discordance.

RESULTS

Among 352 placentas, 97 % (340) had intertwin AV anastomoses, and 50 % (176) were from pregnancies with selective growth restriction. The AV ratio, AA, VV, total AV areas, and cord insertion discordance negatively correlated with BWR/PR. Multivariable linear regression confirmed the independent negative association between BWR/PR and the AV ratio, suggesting that a larger shared circulation benefits the twin with the smaller placental part. Type III sFGR placentas exhibited the highest AV ratio, resulting in the lowest BWR/PR.

DISCUSSION

A larger shared circulation mitigates the impact of an unequally divided placenta on fetal growth. This effect surpasses the influence of AA and VV diameters and is most prominent in Type III sFGR placentas.

A Spontaneous Tubal Heterotopic Triplet Pregnancy Resulting in Viable Twin Deliveries

There are limited U.S. reports of spontaneous triplet heterotopic pregnancies discussing both maternal and fetal outcomes. A 34-year-old patient at 7 weeks of gestation presented to the emergency department with abdominal pain. She was diagnosed with a spontaneous heterotopic triplet pregnancy, consisting of a twin monochorionic-diamniotic intrauterine gestation and a ruptured left ectopic pregnancy. She underwent a laparoscopic unilateral salpingectomy. Her antepartum course was complicated by gestational diabetes mellitus and fetal growth restriction. Delivery of liveborn twins was via a cesarean delivery at 32 weeks. Timely intervention and management of a ruptured spontaneous triplet heterotopic pregnancy can result in a viable twin delivery with overall favorable maternal and newborn outcomes, although long-term implications due to prematurity and other twin sequelae exist.

Clinical outcomes of fetal selective reduction in dichorionic triplet pregnancies

BACKGROUND

It is recommended to reduce triplet pregnancy containing monochorionic (MC) twins to singleton. Given that some couples with infertility are eager to retain twins, better strategy is needed to avoid obstetrical risks and satisfy their strong wish. This retrospective observational study aimed to investigate the outcomes of triplet pregnancy reduction.

METHODS

Subjects with triplet pregnancies who underwent selective reduction between 2016 and 2019 at our hospital were enrolled. A total of 66 subjects with dichorionic triplet (DCT) with MC twins and an MC singleton were divided into two groups: group A (N = 38), reduced to dichorionic diamniotic (DCDA) twins; group B (N = 28), reduced to MC diamniotic (MCDA) twins. Obstetrical and perinatal outcomes were compared between groups.

RESULTS

Group A had significantly lower rates of early miscarriage (0% vs 14.3%, p = 0.028), cesarean section (81.6% vs 100%, p = 0.041), and late premature delivery (21.1% vs 45.4%, p = 0.047) than group B. Significantly higher rates of full-term delivery (71% vs 36.4%, p = 0.009) and take-home baby (100% vs 78.6%, p = 0.004), and higher gestational age at delivery (median: 38 [36.9, 39.0] vs 35.8 [34.4, 37.0] weeks, p < 0.001), total neonatal weight (2899.7 ± 647.6 vs 2354.4 ± 651.8 g, p < 0.001), weight of twins (2550 vs 2350 g, p = 0.039), and weight of larger neonate in twins (2790 vs 2500 g, p = 0.045) were observed in group A compared to group B.

CONCLUSION

DCT reduced to DCDA twins confers better pregnancy outcomes than into MCDA twins. This might benefit for triplet pregnancy subjects who strongly want to retain fraternal twins.

Monochorionic Twins: TTTS, TAPS, and Selective Fetal Growth Restriction

With an increasing incidence of twin gestations, understanding the inherent risks associated with these pregnancies is essential in modern obstetrics. The unique differences in placentation in monochorionic twins leads to unique complications, including twin-to-twin transfusion syndrome, the twin anemia-polycythemia sequence, and selective fetal growth restriction. Not only does the understanding of the monochorionic placenta lead to an understanding of the pathophysiology of the complications of monochorionic twins, but it also has led to the development of highly effective directed fetal therapy via fetoscopic laser coagulation used in twin-to-twin transfusion syndrome.

The impact of placental anastomoses and umbilical cord insertions' sites on monochorionic twin pregnancy outcomes: Evidence from color-dye injection studies

INTRODUCTION

Our knowledge of monochorionic pregnancies' complications is largely based on the extensive ongoing research on monochorionic placental structure. Previous studies on the concordance of umbilical cord insertions are limited. This study aimed to evaluate placental anastomoses and cord insertions as independent risk factors for neonatal adverse outcomes.

METHODS

This was a prospective study conducted at Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy from April 2021 to December 2022. Seventy-six women with a monochorionic pregnancy were enrolled at their first-trimester scan. After delivery, all placentas that were confirmed to be monochorionic were analyzed according to standard protocols, including those of complicated monochorionic twin pregnancies. The primary outcomes were a Composite Monochorionic Pregnancy Outcome (CMPO) and a Composite Neonatal Adverse Outcome (CNAO). The secondary outcome was the birth weight discordance between the neonates.

RESULTS

The CMPO occurred in 15.8 % pregnancies, and the CNAO occurred in 67.1 % pregnancies. The analysis confirmed a significant association between velamentous cord insertions and neonatal adverse events (p = 0.003). Also, a significant positive association (p = 0.0326) between twin birth weight discordance and discordance in twins umbilical cord insertions' sites was found. No significant association between the number and type of the anastomoses and both the CMPO or CNAO was detected.

DISCUSSION

Our data suggest that the routine sonographic assessment of umbilical cords' insertion sites during the first trimester could be helpful in predicting fetal and neonatal adverse events. We believe that this sonographic assessment should start to be implemented in our routine care of monochorionic pregnancies.

Selective intrauterine growth restriction without concomitant twin-to-twin transfusion syndrome, natural history, and risk factors for fetal death: A systematic review and meta-analysis

OBJECTIVE

This study aimed to evaluate the natural history of selective intrauterine growth restriction in monochorionic twin pregnancies based on the Gratacós classification, including progression of, improvement in, or stability of umbilical artery Dopplers and progression to twin-to-twin transfusion syndrome or twin anemia polycythemia syndrome. We also aimed to investigate risk factors for smaller twin demise.

DATA SOURCES

A systematic search was performed to identify relevant studies published in English up to June 2022 using the databases PubMed, Scopus, and Web of Science STUDY ELIGIBILITY: We used retrospective and prospective studies published in English that reported on selective intrauterine growth restriction without concomitant twin-to-twin transfusion syndrome.

STUDY APPRAISAL AND SYNTHESIS METHODS

Articles that investigated selective intrauterine growth restriction progression and outcomes by umbilical artery Doppler end-diastolic flow (Gratacós classification) were included. Type I included selective intrauterine growth restriction cases with positive end-diastolic flow, type II included those cases with persistently absent end-diastolic flow, and type III included cases with intermittent absent or reversed end-diastolic flow. Pregnancies in which a diagnosis of twin-to-twin transfusion syndrome or twin anemia polycythemia sequence was made before the diagnosis of selective intrauterine growth restriction were not included in the analysis. A random effects model was used to pool the odds ratios and the corresponding 95% confidence intervals. Heterogeneity was assessed using the I2 value.

RESULTS

A total of 17 studies encompassing 2748 monochorionic pregnancies complicated by selective intrauterine growth restriction were included in the analysis. The incidence of stable, deteriorating, or improving umbilical artery Dopplers in type I cases was 68% (95% confidence interval, 26-89), 23% (95% confidence interval, 7-40), and 9% (95% confidence interval, 0.0-100), respectively. In type II cases, the incidence was 40% (95% confidence interval, 18-81), 50% (95% confidence interval, 23-82), and 10% (95% confidence interval, 4-37), respectively, and in type III cases, the incidence was 55% (95% confidence interval, 2-99), 23% (95% confidence interval, 9-43), and 22% (95% confidence interval, 6-54), respectively. The risk for progression to twin-to-twin transfusion syndrome was comparable between type I (7%) and type III (9%) cases and occurred in 4% (95% confidence interval, 0-67) of type II cases with no significant subgroup differences. Progression to twin anemia polycythemia syndrome was highest in type I cases (12%) and comparable between type II (2%) and III (1%) cases with no significant subgroup differences. Risk factors for smaller twin demise were earlier gestational age at diagnosis (mean difference, -2.69 weeks; 95% confidence interval, -4.94 to -0.45; I2, 45%), larger intertwin weight discordance (mean difference, 34%; 95% confidence interval, 1.35-5.38; I2, 28%), deterioration of umbilical artery Dopplers for each of type II and III cases (odds ratio, 3.05; 95% confidence interval, 1.36-6.84; I2, 24%; and odds ratio, 4.5; 95% confidence interval, 2.31-8.77; I2, 0.0%, respectively), and absent or reversed ductus venosus a-wave for each of type II and III cases (odds ratio, 3.35; 95% confidence interval, 2.28-4.93; I2, 0.0%; and odds ratio, 2.36; 95% confidence interval, 1.08-5.13; I2, 0.0%, respectively). Progression to twin-to-twin transfusion syndrome was not significantly associated with smaller twin demise for each of type II and III selective intrauterine growth restriction cases.

CONCLUSION

These findings improve our understanding of the natural history of the types of selective intrauterine growth restriction and of the predictors of smaller twin demise in type II and III selective intrauterine growth restriction cases. The current data provide vital counseling points and support the need for modifications of the current selective intrauterine growth restriction classification system to include the variations in umbilical artery and ductus venosus Dopplers to better identify a cohort that might benefit from fetal intervention for which future multicenter prospective randomized trials are needed.

Chorionicity-associated variation in metabolic phenotype of cord blood in twin

BACKGROUND

Monochorionic (MC) twins present a higher incidence of unfavorable clinical perinatal outcomes than dichorionic (DC) twins, often in association with placental vascular anastomosis. In this study, we profiled the umbilical cord plasma metabolomes of uncomplicated MC and DC twin pregnancies and related these to several offspring outcomes, previously associated with birthweight.

METHODS

Umbilical vein blood samples were collected at birth from 25 pairs of uncomplicated MC twins and 24 pairs of uncomplicated DC twins. The samples were subjected to gas chromatography-mass spectrometry-based metabolomics. 152 metabolites were identified from the cord plasma samples of MC and DC twins. Partial least squares discriminant analysis and pathway analysis were performed to compare within DC/MC twin pairs and between DC and MC twins. A generalized estimating equation (GEE) model was utilized to explore the correlation between metabolic differences and birthweight discordance within and between twin pairs.

RESULTS

Our study revealed clear differences between the metabolite profiles of umbilical cord plasma of MC and DC twins. Metabolite profiles in MC within twin pairs and DC within twin pairs were characterized by the differences in 2 - hydroxyglutaramic acid levels and nicotinamide levels, respectively. The metabolic pathways of GSH, tryptophan, and fatty acid metabolism, were significantly downregulated in MC twins compared to DC twins. In addition, the concentration of caffeine and decamethyl-cyclopentasiloxane (D5) was positively correlated with birthweight in MC and DC twins.

CONCLUSION

This study demonstrated that the altered metabolites in umbilical plasma made contributions to the different chorionicities between uncomplicated MC twins and DC twins. The chorionicity of twins seems to affect the metabolic cross-talk between co-twin pairs and be related to birthweight discordance of twins.

Developments in functional imaging of the placenta

The placenta is both the literal and metaphorical black box of pregnancy. Measurement of the function of the placenta has the potential to enhance our understanding of this enigmatic organ and serve to support obstetric decision making. Advanced imaging techniques are key to support these measurements. This review summarises emerging imaging technology being used to measure the function of the placenta and new developments in the computational analysis of these data. We address three important examples where functional imaging is supporting our understanding of these conditions: fetal growth restriction, placenta accreta, and twin-twin transfusion syndrome.

Prevalence and Factors Associated With Intertwin Birth Weight Discordance Among Same-Sex Twins in Lombardy, Northern Italy

This population-based cohort study investigated the prevalence, potential risk factors, and consequences of birth weight discordance (BWD) among same-sex twins. We retrieved data from the automated system of healthcare utilization databases of Lombardy Region, Northern Italy (2007-2021). BWD was defined as 30% or more disparity in birth weights between the larger and the smaller twin. Multivariate logistic regression was used to analyze the risk factors of BWD in deliveries with same-sex twins. In addition, the distribution of several neonatal outcomes was assessed overall and according to BWD level (i.e., ≤20%, 21-29, and ≥30%). Finally, a stratified analysis by BWD was performed to assess the relationship between assisted reproductive technologies (ART) and neonatal outcomes. We identified 11,096 same-sex twin deliveries; 556 (5.0%) pairs of twins were affected by BWD. Multivariate logistic regression analysis showed that maternal age ≥35 years (OR 1.26, 95% CI [1.05,5.51]), low level of education (OR 1.34, 95% CI [1.05, 1.70]), and ART (OR 1.16, 95% CI [0.94, 1.44], almost significant due to the low power) were independent risk factors for BWD in same-sex twins. Conversely, parity (OR 0.73, 95% CI [0.60, 0.89]) was inversely related. All the adverse outcomes observed were more common among BWD pairs than non-BWD ones. Instead, a protective effect of ART was observed for most neonatal outcomes considered among BWD twins. Our results suggest that conception after ART increases the risk of developing a high disparity between the weights of the two twins. However, the presence of BWD may complicate twin pregnancies, compromising neonatal outcomes, regardless of the modality of conception.

Prediction of dual survival following fetoscopic laser photocoagulation for twin-twin transfusion syndrome

OBJECTIVE

To develop a model based on factors available at the time of diagnosis of twin-twin transfusion syndrome (TTTS) for predicting the probability of dual twin survival following fetoscopic laser photocoagulation (FLP) using a machine-learning algorithm.

METHODS

This was a retrospective study of data collected at two university-affiliated tertiary fetal centers between 2012 and 2021. The cohort included monochorionic diamniotic twin pregnancies complicated by TTTS that underwent FLP. Data were stratified based on survival 30 days after delivery, and cases with dual survival were compared to those without dual survival. A random forest machine-learning algorithm was used to construct a prediction model, and the relative importance value was calculated for each parameter that presented a statistically significant difference between the two study groups and was included in the model. The holdout method was applied to check overfitting of the random forest algorithm. A prediction model for dual twin survival 30 days after delivery was presented based on the test set.

RESULTS

The study included 537 women with monochorionic diamniotic twin pregnancy, of whom 346 (64.4%) had dual twin survival at 30 days after delivery and were compared with 191 (35.6%) cases that had one or no survivors. Univariate analysis demonstrated no differences in demographic parameters between the groups. At the time of diagnosis, the dual-survival group had lower rates of estimated fetal weight (EFW) < 10th centile for gestational age in the donor twin (56.4% vs 69.4%; P = 0.004), intertwin EFW discordance > 25% (40.8% vs 56.5%; P = 0.001) and anterior placenta (40.5% vs 50.0%; P = 0.034). Comparison of Doppler findings between the two groups demonstrated significant differences in the donor twin, with a lower rate of pulsatility index (PI) > 95th centile in the umbilical artery and ductus venosus and a lower rate of PI < 5th centile in the fetal middle cerebral artery in the dual-survival group. Relative importance values for each of these six parameters were calculated, allowing the construction of a prediction model with an area under the receiver-operating-characteristics curve of 0.916 (95% CI, 0.887-0.946).

CONCLUSIONS

We developed a predictive model for dual survival in monochorionic twin pregnancies following FLP for TTTS, which incorporates six variables obtained at the time of diagnosis of TTTS, including donor EFW < 10th centile, intertwin EFW discordance > 25%, anterior placenta and abnormal PI in the umbilical artery, ductus venosus and middle cerebral artery of the donor twin. This clinically applicable tool may improve treatment planning and patient counseling. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Twin Anemia-Polycythemia Sequence (TAPS): From Basic Research to Clinical Practice

Twin pregnancy is associated with an increased risk of perinatal and maternal complications, and early establishment of the chorionicity type defines this risk. In monochorionic (MC) pregnancies, the fetuses share the same placental mass and exhibit vascular anastomoses crossing the intertwin membrane, and the combination and pattern of anastomoses determine the primary clinical picture and occurrence of future complications. Twin Anemia-Polycythemia Sequence (TAPS) was first described in 2006 after fetoscopic laser surgery in twin-to-twin transfusion syndrome (TTTS) twins, and in 2007, the first spontaneous cases were reported, recognizing TAPS as an individualized vascular identity in fetofetal transfusion syndromes. There are two types of TAPS: spontaneous (3-5%) and iatrogenic or postlaser (2-16%). TAPS consists of small diameter arteriovenous anastomoses (<1 mm) and low-rate, small-caliber AA anastomoses in the absence of amniotic fluid discordances. There are certain antenatal and postnatal diagnostic criteria, which have progressively evolved over time. New, additional secondary markers have been proposed, and their reliability is being studied. The best screening protocol for TAPS in MC twins is still a matter of debate. This review provides a survey of the relevant literature on the epidemiology, vascular pathophysiology, underlying hemodynamic factors that regulate mismatched vascular connections, and diagnostic criteria of this condition. The aim is to increase awareness and knowledge about this recently identified and frequently unrecognized and misdiagnosed pathology.

Fetoscopic laser surgery for twin-to-twin transfusion syndrome in DCTA triplets compared to MCDA twins: collaborative study and literature review

OBJECTIVE

To compare the outcomes of dichorionic triamniotic (DCTA) triplets with that of monochorionic diamniotic (MCDA) twin gestations undergoing fetoscopic laser surgery (FLS) for treatment of twin-to-twin transfusion syndrome (TTTS).

METHODS

Retrospective cohort study of prospectively collected data of consecutive DCTA triplet and MCDA twin pregnancies with TTTS that underwent FLS at two fetal treatment centers between 2012 and 2020. Preoperative, operative and, postoperative variables were collected. Perinatal outcomes were investigated. Primary outcome was survival to birth and to neonatal period. Secondary outcomes were gestational age (GA) at birth and procedure-to-delivery interval. Literature review was conducted in which PubMed, Web of Science, and Scopus were searched from inception to September, 2020.

RESULTS

Twenty four sets of DCTA triplets were compared to MCDA twins during the study period. There were no significant differences in survival (no survivor, single, or double survivors) to birth and to the neonatal period of the MC twin pairs of the DCTA triplets vs MCDA twins. Median GA at delivery was approximately three weeks earlier in DCTA triplets compared to MCDA twins (28.4 weeks vs 31.4 weeks, p = .035, respectively). Rates of preterm birth (PTB) less than 32 and less than 28 weeks were significantly higher in DCTA triplets compared to twins (<32 weeks: 70.8% vs 51.1%, p = .037, respectively, and <28 weeks: 37.5% vs 20.8%, p = .033, respectively).

CONCLUSION

Perinatal survival including fetal and neonatal are comparable between DCTA triplets and MCDA twins. However, this might have resulted from the small sample size of the DCTA triplets. GA at delivery is earlier in triplets, which could be due to the nature of triplet gestation rather than to the laser procedure itself.

Twin to Twin Transfusion Syndrome: A Case Report

Twin-twin transfusion syndrome occurs in multiple gestations and involves a chronic flow of blood from one twin to another twin and is a rare entity. We present a case of 32-years-old primigravida with a twin pregnancy who presented with increasing abdominal girth inappropriate with her gestational age at 21 weeks of her pregnancy. Ultrasound findings were suggestive of twin-twin transfusion syndrome. The patient was provided with treatment options but due to polyhydramnios and short cervix, the patient went into spontaneous labour the same day with a poor pregnancy outcome. Twin-twin transfusion syndrome leads to a high rate of perinatal morbidity due to its poorly understood aetiology and difficulty in diagnosing and treatment. Early diagnosis during antenatal ultrasound is important in reducing morbidity and mortality rates.

Keywords

case reports; fetoscopy; oligohydramnios; polyhydramnios; twins.

Maternal Inherited Thrombophilia in Monochorionic Twin Pregnancy with Twin-Twin Transfusion Syndrome

BACKGROUND

To study the frequency of inherited thrombophilia in monochorionic twin pregnancies with twin-twin transfusion syndrome (TTTS).

METHODS

At the Department of Obstetrics of the Polytechnic University of Marche (Ancona, Italy) a population of monochorionic diamniotic pregnant women was selected retrospectively. After termination of the pregnancy, genotyping for Factor I, Factor V Leiden, Factor II and Methylenetetrahydrofolate Reductase (MTHFR), as well as activities of the plasma proteins C and S, was performed.

RESULTS

Regarding the 32 patients with TTTS, from a cohort of 104 monochorionic pregnancies recruited, at least one thrombophilic defect was more frequent (OR: 3.24), and the allele polymorphism frequency was higher for Factor I (OR: 4.4) and for Factor V Leiden (OR: 11.66).

CONCLUSIONS

Maternal inherited thrombophilia, possibly also inherited from monochorial fetuses, may result in impaired development of the placental vascular architecture. This inheritance hypothesis may explain why only a fraction of monochorionic diamniotic twins develop TTTS.

Molecular Mechanisms Underlying Twin-to-Twin Transfusion Syndrome

Twin-to-twin transfusion syndrome is a unique disease and a serious complication occurring in 10–15% of monochorionic multiple pregnancies with various placental complications, including hypoxia, anemia, increased oxidative stress, and ischemia-reperfusion injury. Fetoscopic laser photocoagulation, a minimally invasive surgical procedure, seals the placental vascular anastomoses between twins and dramatically improves the survival rates in twin-to-twin transfusion syndrome. However, fetal demise still occurs, suggesting the presence of causes other than placental vascular anastomoses. Placental insufficiency is considered as the main cause of fetal demise in such cases; however, little is known about its underlying molecular mechanisms. Indeed, the further association of the pathogenic mechanisms involved in twin-to-twin transfusion syndrome placenta with several molecules and pathways, such as vascular endothelial growth factor and the renin–angiotensin system, makes it difficult to understand the underlying pathological conditions. Currently, there are no effective strategies focusing on these mechanisms in clinical practice. Certain types of cell death due to oxidative stress might be occurring in the placenta, and elucidation of the molecular mechanism underlying this cell death can help manage and prevent it. This review reports on the molecular mechanisms underlying the development of twin-to-twin transfusion syndrome for effective management and prevention of fetal demise after fetoscopic laser photocoagulation.

Umbilical venous diameter and flow in monochorionic diamniotic twin pregnancy: association with placental sharing and fetal demise

OBJECTIVE

To examine the association of umbilical venous diameter and flow in monochorionic diamniotic twin pregnancy with placental sharing and fetal demise.

METHODS

This was a prospective longitudinal cohort study of a consecutive series of monochorionic diamniotic twin pregnancies that underwent ultrasound assessments at 12, 16, 20 and 28 weeks' gestation. Fetal biometry (crown-rump length at 12 weeks or estimated fetal weight (EFW) thereafter) and cord insertion sites were recorded at each visit, as well as the diameter of the umbilical vein (UV) in both the intra-abdominal part and a free loop of the umbilical cord. Time-averaged maximum velocity in the intra-abdominal part of the UV was measured to calculate UV-flow. Univariate and multivariate linear regression analyses were performed to assess the relationship between intertwin ratios of these variables and placental sharing at 12, 16, 20 and 28 weeks' gestation. Placental sharing was calculated by dividing the larger by the smaller placental share, as measured on placental injection studies after birth. Additionally, the Mann-Whitney U-test and receiver-operating-characteristics-curve analysis were used to explore the relationship between the occurrence of fetal demise and intertwin differences in fetal biometry, cord insertion sites, UV diameters and flow at 12, 16, 20 and 28 weeks.

RESULTS

Of 200 consecutive monochorionic twin pregnancies enrolled, injection studies were performed in 165 (82.5%) placentas. On univariate analysis, intertwin differences in fetal biometry, cord insertions and UV variables were associated significantly with placental sharing at 12, 16, 20 and 28 weeks' gestation. On multivariate analysis, intertwin differences in fetal biometry, cord insertions and all three UV variables remained associated significantly with placental sharing at 12 and 16 weeks. However, at 20 and 28 weeks, only the intertwin EFW ratio was associated consistently with placental sharing. Fetal demise of one or both twins complicated 26 (13.0%) pregnancies. Differences in EFW and cord insertion sites were not associated significantly with fetal demise, while at 16 weeks, differences in intra-abdominal UV diameter and flow were associated with an increased risk of subsequent fetal demise.

CONCLUSIONS

At 12 and 16 weeks' gestation, intertwin differences in UV diameter and flow reflect placental sharing more accurately than do differences in fetal growth and cord insertion sites. At 16 weeks, discordance in intra-abdominal UV diameter and flow is also associated with an increased risk of fetal demise. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Single fetal demise following fetoscopic ablation for twin-to-twin transfusion syndrome-cohort study, systematic review, and meta-analysis

BACKGROUND

Several studies have assessed preoperative and operative factors associated with fetal demise after laser for TTTS, yet these findings are not completely conclusive.

OBJECTIVE

This study aimed to identify risk factors for single fetal demise (recipient and donor twins) after fetoscopic laser photocoagulation for twin-to-twin transfusion syndrome.

STUDY DESIGN

We searched PubMed, Scopus, and Web of Science systematically from the inception of the database to June 2020. We conducted a systemic review on studies investigating risk factors for fetal demise (donor and/or recipient) after fetoscopic laser photocoagulation in monochorionic pregnancies complicated with twin-to-twin transfusion syndrome. Initially, we investigated the cohort of women with twin-to-twin transfusion syndrome that underwent fetoscopic laser photocoagulation at our 2 high-volume fetal centers between 2012 and 2020 to identify risk factors for donor demise and recipient demise. Furthermore, we conducted a systematic review of the literature to better characterize these factors. Among studies that met the entry criteria, multiple preoperative and operative factors were tabulated. The random-effect model was used to pool the standardized mean differences or odds ratios and corresponding 95% confidence intervals. Heterogeneity was assessed using the I² value.

RESULTS

A total of 514 pregnancies with twin-to-twin transfusion syndrome managed with fetoscopic laser photocoagulation were included in the final analysis. Following the logistic regression, factors that remained significant for donor demise were selective fetal growth restriction (odds ratio, 1.9; 95% confidence interval, 1.3-2.8; P=.001) and umbilical artery blood flow with absent or reversed end-diastolic velocity of the donor (odds ratio, 2.06; 95% confidence interval, 1.2-3.4; P=.004). A significant factor associated with recipient demise was absent or reversed a-wave in the ductus venosus of the recipient (odds ratio, 1.74; 95% confidence interval, 1.07-3.13; P=.04). Data from 23 studies and our current cohort were included. A total of 4892 pregnancies with twin-to-twin transfusion syndrome managed with fetoscopic laser photocoagulation were analyzed for risk factors for donor demise, and 4594 pregnancies with twin-to-twin transfusion syndrome were analyzed for recipient demise. Among studies, the overall incidence rates ranged from 10.9% to 35.8% for donor demise and 7.3% to 24.5% for recipient demise. Significant risk factors for donor demise were intertwin estimated fetal weight discordance of >25% (odds ratio, 1.86; 95% confidence interval, 1.44-2.4; I², 0.0%), selective fetal growth restriction (odds ratio, 1.78; 95% confidence interval, 1.4-2.27; I², 0.0%), twin-to-twin transfusion syndrome stage III (odds ratio, 2.18; 95% confidence interval, 1.53-3.12; I², 0.0%), umbilical artery blood flow with absent or reversed end-diastolic velocity of the donor (odds ratio, 2.31; 95% confidence interval, 1.9-2.8; I², 23.7%), absent or reversed a-wave in the ductus venosus of the donor (odds ratio, 1.83; 95% confidence interval, 1.45-2.3; I², 0.0%), and presence of arterioarterial anastomoses (odds ratio, 2.81; 95% confidence interval, 1.35-5.85; I², 90.7%). Sequential selective coagulation was protective against donor demise (odds ratio, 0.31; 95% confidence interval, 0.16-0.58; I², 0.0%). Significant risk factors for recipient demise were twin-to-twin transfusion syndrome stage IV (odds ratio, 2.18; 95% confidence interval, 1.01-4.6; I², 16.5%), umbilical artery blood flow with absent or reversed end-diastolic velocity of the recipient (odds ratio, 2.68; 95% confidence interval, 1.91-3.74; I², 0.0%), absent or reversed a-wave in the ductus venosus of the recipient (odds ratio, 2.37; 95% confidence interval, 1.55-3.64; I², 60.2%), and middle cerebral artery peak systolic velocity of >1.5 multiple of the median (odds ratio, 3.06; 95% confidence interval, 1.36-6.88; I², 0.0%).

CONCLUSION

Abnormal blood flow patterns represented by abnormal Doppler studies and low fetal weight were associated with single fetal demise in women with twin-to-twin transfusion syndrome undergoing laser therapy. Although sequential selective coagulation was protective against donor demise, the presence of arterioarterial anastomoses was considerably associated with donor demise. This meta-analysis extensively investigated the association of a wide range of preoperative and operative factors with fetal demise. These findings may be important inpatient counseling, in further understanding the disease, and perhaps in improving surgical techniques.

Neonatal and Long-Term Prognosis of Monochorionic Diamniotic Pregnancies Complicated by Selective Growth Restriction

Background: There are few data concerning the neonatal and long-term prognosis of monochorionic biamniotic twin pregnancies (MCBA) complicated by selective intrauterine growth restriction (sIUGR). The aim of the study is to assess the neurological outcomes at two years of age of these newborns and compares these outcomes to those of newborns resulting from intrauterine growth restriction (IUGR) pregnancies. Methods: The study focuses on a cross-sectional prospective cohort of patients treated between 2012 and 2019 in Marseille, France. The primary endpoint is the overall score of the Ages and Stages questionnaires (ASQ) at two years, which assesses the global neurodevelopment. The secondary endpoint is the assessment of neonatal morbi-mortality for both groups (composite endpoint). Results: In total, 251 patients were included in the analysis: 67 in the sIUGR group and 184 in the IUGR group. There was no statistically significant difference in the overall ASQ score at two years but there was the finest motor skills impairment in the IUGR group. The areas most often impaired were communication and fine motor skills. There were no significant differences between the neonatal morbi-mortality of the two groups (adjusted OR = 0.95, p = 0.9). Conclusions: Newborns from MCBA pregnancies with sIUGR appear to have similar overall neurological development to IUGR. Notably, IUGR seems to have the most moderate neurobehavioral disorder (fine motor) as a consequence of impaired antenatal brain development due to placenta insufficiency leading to chronic hypoxia.

Selective vs complete fetoscopic coagulation of vascular equator: a matched comparative study

BACKGROUND

Complete coagulation of the vascular equator (as in the Solomon technique) has been suggested to reduce postoperative complications such as twin anemia polycythemia syndrome and the recurrence of twin-twin transfusion syndrome following fetoscopic laser coagulation of chorionic vessels for twin-twin transfusion syndrome.

OBJECTIVE

We aimed to evaluate the benefit of this technique on perinatal outcomes compared with selective ablation of anastomoses.

STUDY DESIGN

We conducted a monocentric retrospective study comparing selective laser coagulation of anastomoses to the Solomon technique from January 2006 to August 2020. To adjust for potential confounders, the cases operated by selective surgery were matched to the cases operated with the Solomon technique according to the gestational age at laser therapy, placental localization, and Quintero stage using propensity score matching.

RESULTS

With a total of 994 cases, 399 matched pairs were included in the analysis. Compared with selective ablation, the Solomon technique was associated with significantly improved survival: the overall twin survival at delivery and discharge was 72% vs 79% (P=.003) and 69% vs 75% (P=.006), respectively; the double twin survival rate at discharge was 55% vs 65% (P=.02), respectively, and the rate of intrauterine death dropped from 18% to 12% (P=.003), respectively. The Solomon technique significantly reduced the rate of twin anemia polycythemia syndrome (10% vs 4%; P=.02), leading to fewer secondary rescue procedures (13% vs 7.3%; P=.01). However, the Solomon technique was associated with an increased risk of preterm rupture of membranes, especially at early gestational ages (3.8% vs 11%; P<.001 for preterm rupture of membranes <24 weeks). Among the survivors at delivery, both the groups had similar gestational ages at birth. Both neonatal mortality and severe neurologic morbidity were similar in both the groups. However, an increased risk of bronchopulmonary dysplasia was found in the Solomon group (4.5% vs 12%; P<.001).

CONCLUSION

Although the risk of preterm premature rupture of membranes has increased, the introduction of the Solomon technique has significantly improved perinatal outcomes in pregnancies affected with twin-twin transfusion syndrome.

Sonographic evaluation of umbilical cord thickness in monochorionic diamniotic twin pregnancies

OBJECTIVE

To develop a nomogram of the thickness of the umbilical cord (UC) and its components in monochorionic diamniotic (MCDA) twin pregnancies.

METHODS

This prospective longitudinal study involved 47 MCDA twin pregnancies (94 fetuses) between 18 and 33 weeks of gestation. Ultrasound assessments of UC cross-sections and measurements of the umbilical cord area (UCA), the umbilical vein area (UVA), the umbilical artery area (UAA), and the Wharton jelly area (WJA) were made. The UC measurements were correlated with gestational ages. Reference values for the gestational ages of MCDA pregnancies were determined and compared with those of dichorionic twins and singletons. The cases which developed selective intrauterine growth restriction were contrasted with normal cases.

RESULTS

A positive correlation was found between all UC components and gestational age and fetal weight. The UCA of MCDA fetuses was significantly larger than that of DC fetuses (P < 0.001) at the expense of a larger WJA (P < 0.001) and similar to that of singleton pregnancies. The MCDA fetuses with an estimated fetal weight below the 10th percentile had a smaller UCA than fetuses with a normal estimated weight (P < 0.001).

CONCLUSION

The MCDA twins exhibited a thicker UC than that of dichorionic twins. This article is protected by copyright. All rights reserved.

Iatrogenic chorioamniotic separation and septostomy following fetoscopic laser photocoagulation for twin-twin transfusion syndrome

OBJECTIVE

To compare the perinatal outcomes of pregnancies complicated by chorioamniotic separation (CAS) vs septostomy following fetoscopic laser photocoagulation (FLP) for twin-twin transfusion syndrome (TTTS).

METHODS

This was a retrospective cohort analysis of monochorionic diamniotic twin pregnancies with TTTS that underwent FLP at one of two university-affiliated tertiary medical centers between January 2012 and December 2020. CAS and septostomy were diagnosed either during the procedure or by ultrasonography within 24-48 h after FLP. Data on procedure and postprocedure parameters, pregnancy outcomes and survival were collected from the patients' electronic medical records. Pregnancies were stratified according to the presence of CAS, septostomy or neither. Patients diagnosed with both CAS and septostomy were analyzed separately.

RESULTS

Of the 522 women included in the cohort, 38 (7.3%) were diagnosed with CAS, 68 (13.0%) with septostomy and 23 (4.4%) with both CAS and septostomy. The remaining 393 (75.3%) women comprised the control group. Groups did not differ in demographic characteristics. The septostomy group had a lower rate of selective fetal growth restriction than did the CAS and control groups (24.2% vs 36.8% vs 42.7%, respectively; P = 0.017). Moreover, intertwin size discordance was lower in the septostomy group (15.1% vs 23.4% in the CAS group and 25.5% in the control group; P = 0.001). Median gestational age at FLP was significantly lower in the CAS group (19.3 weeks vs 20.4 weeks in controls and 20.9 weeks in the septostomy group; P = 0.049). The rate of delivery prior to 34 weeks was significantly higher in the CAS group (89.2%), followed by the septostomy group (80.9%), compared with the control group (69.0%) (P = 0.006). A secondary analysis demonstrated that patients with both CAS and septostomy presented the highest rates of delivery prior to 34 weeks (100%) and 32 weeks (68.2%).

CONCLUSIONS

CAS and septostomy following laser surgery for TTTS are independently associated with higher rates of preterm delivery. The presence of these two findings in the same patient enhances the risk of prematurity. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

What fetal medicine specialists should know about the monochorionic placenta

Monochorionic twins are at risk of transfusion imbalances as long as they are connected to the shared placenta during their intrauterine journey. This review article addresses the macroscopic examination of the monochorionic placenta at the time of birth and explains placental dye injection studies to document the vascular anastomoses and placental sharing. We elaborate on the different types of anastomoses, the importance of how the placenta is divided between the twins, and the angioarchitecture in twin-twin transfusion syndrome, twin anemia polycythemia sequence and selective fetal growth restriction.

Fetoscopic laser ablation therapy in monochorionic diamniotic twin pregnancies with twin-to-twin transfusion syndrome treated at a single centre over 10 years: a retrospective study

OBJECTIVES

To review experience with fetoscopic laser ablation of placental anastomoses to treat monochorionic diamniotic (MCDA) twin pregnancies complicated by twin-to-twin transfusion syndrome (TTTS) in a single centre over a ten-year period.

METHODS

A retrospective study on 142 MCDA twin pregnancies complicates by TTTS treated with equatorial laser ablation of placental anastomoses (2008-2018). Solomon technique was also applied after 2013. Survival rates, neonatal outcome, intraoperative and post-laser complications were recorded, and prognostic factors analysed.

RESULTS

A total of 133 cases were included in the final analysis; 41 patients were at stage II (30.8%), 73 were at stage III (62.9%), while only 12 (9%) at stage I and two patients (1.7%) at stage IV. Solomon technique was applied in 39 cases (29.3%). Survival of both twins was 51.1% (68/133), of a single twin 20.3% (27/133), and of at least one 71.5% (95/133), with an overall survival of 61.3% (163/266). TAPS and recurrent TTTS occurred in 8 (6%) and 15 (11.3%) patients. Survival of both fetuses increased over time (44.6 vs. 57.3%). A posterior placenta (p<0.003) and the use of the Solomon technique (p<0.02) were more frequent in cases with survival of both fetuses, while TTTS recurrence was significantly associated to the loss of one or two fetuses (p<0.01). Such associations were confirmed at logistic regression analysis.

CONCLUSIONS

Survival of both twins can improve over time and seems to be favourably associated with a placenta in the posterior location and the use of the Solomon technique.

The association between vein-to-vein anastomoses and birth weight discordance in relation to placental sharing in monochorionic twin placentas

INTRODUCTION

This study aims to examine the association between the presence and size of a vein-to-vein (VV) anastomosis and birth weight discordance relative to placental discordance in monochorionic diamniotic twin pregnancies.

METHODS

Placentas of two previous prospective studies were included in this retrospective analysis. After injection with color dye, we measured the placental surface of each twin and VV, artery-to-artery (AA), and artery-to-vein (AV) anastomoses on a digital photograph. We calculated the birth weight ratio (BWR), placental ratio (PR), and birth weight ratio/placenta ratio (BWR/PR), as well as total AV size and net AV transfusion. Placental characteristics were compared between placentas with and without VV anastomoses. We performed univariate analyses to assess the following predictors for BWR/PR: VV size, AA size, total AV size, and net AV transfusion. Multivariate analysis was then performed, including the variables significant in univariate analysis.

RESULTS

We analyzed 247 placentas: 58 (23%) with VV anastomoses and 189 without (77%). The BWR and PR were higher in the group with VV. In contrast, BWR/PR was lower in the group with VV anastomoses than in those without. The size of AA anastomoses was larger in placentas with VV anastomoses than in those without. In univariate analysis, VV size and AA size were significantly associated with BWR/PR. However, in multivariate regression, only VV size remained significantly associated with the BWR/PR.

DISCUSSION

VV anastomoses are associated with a decreased birth weight discordance relative to the placental sharing discordance, independent of the AA anastomoses.

Selective intrauterine growth restriction of monochorionic diamniotic twin pregnancies: What is the neonatal prognosis?

OBJECTIVE

This study compares the neonatal morbidity and mortality of the smallest twins of monochorionic diamniotic (MCDA) pregnancies complicated with selective intrauterine growth restriction (sIUGR) with newborns from singleton pregnancies with intrauterine growth restriction (IUGR).

METHODS

We conducted a retrospective cohort study of patients managed at the prenatal diagnosis center in a single tertiary care hospital between 2012 and 2019. MCDA twin pregnancies complicated with sIUGR (sIUGR group) were compared with singleton pregnancies with IUGR (IUGR group). The primary outcome was the comparison in neonatal morbidity and mortality between the two groups.

RESULTS

The analysis included 251 patients: 67 in the sIUGR group and 184 in the IUGR group. The two groups were comparable in gestational age and birth weight (p > 0.05). Multivariate analysis controlling for factors that may influence neonatal status showed no significant difference between the two groups in any of the neonatal morbidity criteria or the composite morbidity-mortality endpoint (adjusted OR = 0.946 [95% CI = 0.317-2.827]; p = 0.921).

CONCLUSION

Despite supposedly different pathophysiological mechanisms, neonates from MCDA pregnancies complicated with sIUGR and those from singleton pregnancies with IUGR appear to have identical neonatal morbidity and mortality .

Outcomes of laparoscopy-assisted fetoscopic laser photocoagulation for twin-twin transfusion syndrome: An established alternative for inaccessible anterior placenta

OBJECTIVE

To evaluate laparoscopy-assisted fetoscopic laser photocoagulation (FLPC) of placental anastomoses in the treatment of twin-to-twin-transfusion syndrome (TTTS).

STUDY DESIGN

We performed a retrospective cohort study analyzing pregnancies complicated by TTTS who underwent FLPC in a single university-affiliated tertiary medical-center. Outcomes were compared between patients who received laparoscopy-assisted FLPC (study group) and patients who underwent the conventional FLPC technique (control group). Baseline characteristics, sonographic findings, procedure details, and neonatal outcomes were compared between groups.

RESULTS

The cohort included 278 women with 31 in the study group and 247 in the control group. Sonographic parameters, including fetal biometry and TTTS stage, were comparable between study groups. Gestational age at delivery did not differ between the groups (29.22 ± 4.55 weeks in the study group vs. 30.62 ± 4.3 weeks in the control group, p = 0.09). There were no differences in neonatal survival rates at birth and at 30 days between both groups. A subanalysis comparing the laparoscopy-assisted group to only those patients with anterior placenta in the control group, showed a lower rate of incomplete Solomonization in the laparoscopy-assisted study group (3.4% vs. 33%, p = 0.01).

CONCLUSION

Laparoscopy-assisted FLPC is a reasonable and safe option that may be offered in cases of FLPC where an anterior placenta restricts adequate surgical access.

Special Considerations Regarding Antenatal Care and Pregnancy Complications in Dichorionic Twin Pregnancies

Twin pregnancies account for about 3.3% of all deliveries in the United States with the majority of them being dichorionic diamniotic (DCDA). Maternal physiological adaption in twin pregnancies is exaggerated and the rate of almost every maternal and fetal complication is higher when compared to singleton pregnancies. Therefore, twin pregnancies necessitate closer antenatal surveillance by care providers who are familiar with the specific challenges unique to these pregnancies, and there is evidence that following women with twins in a specialized twin clinic can result in improved obstetrical outcomes. The importance of the first antenatal visit in twin pregnancies cannot be over emphasized and should preferably take place early in gestation as it is the optimal period to correctly identify the number of fetuses and the type of placentation (chorionicity and amnionicity). This will allow the patients, families, and caregivers to make the appropriate modifications and to tailor an optimal antenatal follow-up plan. This plan should focus on general recommendations such as weight gain and level of activity, education regarding complications specific to twin pregnancies along with the relevant symptoms and indications to seek care, as well as on close maternal and fetal monitoring. In this review, we summarize available evidence and current guidelines regarding antenatal care in DCDA twin pregnancies.

Elective fetal reduction by radiofrequency ablation in monochorionic diamniotic twins decreases adverse outcomes compared to ongoing monochorionic diamniotic twins

BACKGROUND

Multifetal pregnancy reduction is a technique used to reduce the fetal number to mitigate the risks of adverse outcomes associated with multiple gestations. Monochorionic diamniotic twin pregnancies are subject to unique complications, contributing to adverse pregnancy outcomes. Thus, patients have an option to electively reduce 1 fetus to improve outcomes.

OBJECTIVE

This study aimed to compare outcomes of elective reduction of monochorionic diamniotic twins by radiofrequency ablation to planned ongoing monochorionic diamniotic twins.

STUDY DESIGN

We performed a retrospective review of 315 monochorionic diamniotic twin gestations that underwent first-trimester ultrasound within 1 institution. Planned electively reduced twins were compared with ongoing monochorionic diamniotic twins. All reductions were performed via radiofrequency ablation of the cord insertion site into the fetal abdomen. The primary outcome was preterm birth at <36 weeks' gestation. Secondary outcomes included gestational age at delivery; preterm birth at less than 37-, 34-, 32-, and 28-weeks' gestation; unintended loss; and adverse perinatal outcomes.

RESULTS

Among 315 monochorionic diamniotic pregnancies, 14 (4.4%) underwent elective multifetal pregnancy reduction, and 301 (95.6%) were planned ongoing twins. The mean gestational age of radiofrequency ablation in the elective multifetal pregnancy reduction group was 15.1±0.68 weeks. Patients who underwent elective multifetal pregnancy reduction had significantly higher maternal age (P<.01) and were more likely to be Asian (P<.01). Moreover, they were more likely to have undergone in vitro fertilization (P=.03) and chorionic villus sampling (P<.01). There was a significantly higher rate of term deliveries in the elective radiofrequency ablation group compared with ongoing twins (gestational age, 38 weeks [interquartile range, 36.1-39.1] vs 35.9 weeks [interquartile range, 34.0-36.9]; P<.01). Patients with ongoing pregnancies had a trend of increased rate of preterm birth at <36 weeks' gestation (odds ratio, 3.4; 95% confidence interval, 1.0-12.0; P=.06), a significantly increased risk of preterm birth at <37 weeks' gestation (odds ratio, 8.0; 95% confidence interval, 2.4-26.4; P<.01), and no difference at less than 34-, 32-, or 28- weeks' gestation. All patients who underwent elective radiofrequency ablation had successful pregnancies with no pregnancy losses or terminations. Of ongoing gestations, 36 required procedures, including 16 (5.3%) medically indicated radiofrequency ablation, 14 (4.6%) laser ablation, and 6 (1.9%) amnioreductions. Furthermore, 22 patients (7.3%) with planned ongoing twins had total pregnancy loss at <24 weeks' gestation. Notably, 12 patients (4.0%) had unintended loss of 1 fetus before 24 weeks' gestation in the ongoing pregnancy cohort, and 12 patients (4.0%) had unintended loss of both fetuses before 24 weeks' gestation. Moreover, 5 patients (1.7%) in the ongoing pregnancy group had intrauterine fetal demise at >24 weeks' gestation and 10 patients (3.3%) electively terminated both fetuses. There was no significant difference in loss rates between the 2 groups.

CONCLUSION

In this study of monochorionic diamniotic twins, patients who elected to undergo multifetal pregnancy reduction had significantly lower rates of preterm birth at <37 weeks and a lower trend of preterm birth at <36 weeks' gestation without an increased risk of pregnancy loss. Median gestational age at delivery was significantly higher in the elective multifetal pregnancy reduction group (38 weeks) than in the ongoing pregnancy group (35.9 weeks). Further research is needed to clarify if multifetal pregnancy reduction improves long-term outcomes.

Outcomes of Monochorionic, Diamniotic Twin Pregnancies with Prenatally Diagnosed Intertwin Weight Discordance

OBJECTIVE

Monochorionic, diamniotic (MCDA) twin pairs are predisposed to various pregnancy complications due to the unique placental angioarchitecture of monochorionicity. Few studies have evaluated the outcomes of weight-discordant MCDA pairs without selective fetal growth restriction (SFGR) or the risk factors for development of SFGR. This study aims to describe the natural history of expectant, noninvasive management of weight-discordant MCDA twins and to evaluate risk factors associated with progression to SFGR.

STUDY DESIGN

This was a retrospective cohort study at a single, tertiary care center in the United States. All MCDA twins with isolated intertwin weight discordance (ITWD) ≥ 20% diagnosed before 26 weeks' gestational age (GA) were included. The primary outcome of descriptive analyses was overall pregnancy outcome, incorporating both survival to delivery and GA at delivery, as defined by the North American Fetal Therapy Network. The secondary outcome was SFGR in one twin (defined as estimated fetal weight < 10% for GA) and factors associated with this progression. Only those with fetal ultrasound (US) within 4 weeks of delivery were included in this secondary analysis.

RESULTS

Among 73 MCDA pairs with ITWD, 73% had a good pregnancy outcome, with dual live delivery at a median GA of 33 weeks. Among the 34 pairs with adequate US follow-up, 56% developed SFGR. There were no differences in GA at delivery or discordance at birth between those who did and those who did not develop SFGR. There was a nonsignificant association between increasing ITWD at diagnosis and subsequent development of SFGR.

CONCLUSION

Expectant, noninvasive management can be considered in MCDA twin pregnancies with ITWD ≥ 20% diagnosed before 26 weeks. This approach is associated with a good pregnancy outcome in the majority of cases, even after the development of SFGR in the smaller twin.

KEY POINTS

· Nearly 75% of weight-discordant mo/di twins have a good pregnancy outcome.. · Weight-discordant mo/di twins deliver at a mean gestational age of 33 weeks without invasive therapy.. · Noninvasive management should be considered for weight-discordant mo/di twins..

In vitro simulation of acute feto-fetal transfusion in case of single intrauterine fetal death in monochorionic twins

INTRODUCTION

Thanks to shared circulation in monochorionic twins, single intrauterine fetal death (IUD) may lead to acute feto-fetal transfusion (aFFTR). The objective of the study was to describe our model of aFFTR simulation after IUD in monochorionic (MC) twins.

METHODS

Prospective study analyzed 99 fresh MC placentas with the physiological course. A specially designed protocol was used for the preparation and analysis of the placentas. A pair of infusion sets fixed together using a mechanical mercury sphygmomanometer cuff was connected to the cannulated umbilical arteries. The tonometer was pressurized up to 30 and 40 mmHg. A positive finding of aFFTR was determined as the amount exceeding 1 ml of dye flowed out of the umbilical cord simulating a dead fetus. The number and types of anastomoses, types, and distances between cords insertions, and the size of the placental areas for each fetus were also statistically analyzed. The placental angioarchitecture with and without proven aFFTR was statistically compared, odds ratio (OR) and multivariable logistic analysis were performed.

RESULTS

A total of 49/99 (49.5%) cases of aFFTR was proven, and the average transfusion time of 1 ml was 30 s (19-46 s). aFFTR was present in 49/78 (62.8%) of placentas with arterio-arterial (AA) anastomosis. The median diameter of AA anastomoses with the present, and absent aFFTRF was 2.0 mm and 1.0 mm, respectively. The proven interfetal transfusion was 8%, 31%, and 61% in AA anastomoses with a diameter below 0,5 mm, 0,5-1,5 mm, and above 1,5 mm, respectively (p < 0,001). AA anastomoses diameter >1.5 mm had OR of 44.2 (95% CI 5.54-352.39). In the case of coexistence of AA anastomosis and umbilical cord distance ≤5th percentile, the aFFTRF occurred in 90.9%.

DISCUSSION

The potential risk of aFFTR in monochorionic twins is mainly due to the presence and nature of AA anastomoses. The diameter and length of the vessels play a crucial role, which is clinically related to the distance of the umbilical cords insertions.

Perinatal outcome of monochorionic diamniotic twin pregnancy complicated by selective intrauterine growth restriction according to umbilical artery Doppler flow pattern: single-center study using strict fetal surveillance protocol

OBJECTIVE

To determine the perinatal outcome of monochorionic diamniotic (MCDA) twin pregnancies complicated by selective intrauterine growth restriction (sIUGR), which were classified according to the umbilical artery (UA) Doppler flow pattern of the IUGR twin.

METHODS

This was a retrospective cohort study of all MCDA twin pregnancies diagnosed with sIUGR and managed at a single tertiary referral center between 2012 and 2018. Cases were classified according to the UA Doppler flow pattern of the IUGR twin as Type I (positive end-diastolic flow), Type II (persistently absent/reversed end-diastolic flow) or Type III (intermittently absent/reversed end-diastolic flow). Patients with Type-II or -III sIUGR were hospitalized at 26-28 weeks of gestation for increased fetal surveillance. Perinatal and immediate and long-term neurodevelopmental outcomes were stratified according to the UA Doppler flow pattern at the final examination. Intact survival rate was defined as the number of infants surviving without neurological impairment, divided by the total number of fetuses. Composite adverse outcome, defined as any mortality, presence of severe brain lesions on postnatal transcranial ultrasound or severe neurological morbidity, was also assessed.

RESULTS

Of 88 MCDA twin pregnancies with sIUGR included in the study, 28 underwent selective termination by cord occlusion using radiofrequency ablation, resulting in a perinatal survival rate of 89.3% and a median gestational age (GA) at delivery of 33.8 (interquartile range (IQR), 28.8-38.2) weeks for the large cotwin. Expectant management was employed in 60 cases. In 26 (43.3%) cases in the expectant-management group, the classification according to the UA Doppler flow pattern changed during gestation, resulting in 26 (43.3%) cases of Type-I, 22 (36.7%) cases of Type-II and 12 (20.0%) cases of Type-III sIUGR at the final examination. The perinatal survival rate of both twins with sIUGR Types I, II and III at the final examination was 100%, 81.8% and 75.0%, respectively (P = 0.04). Two cases of double fetal death and one case of single fetal death occurred 1-4 weeks after the Doppler pattern had changed from Type I or Type II to Type III. The median GA at delivery was 34.8 (IQR, 33.1-35.7) weeks in Type I, 30.3 (IQR, 28.6-32.1) weeks in Type II and 32.0 (IQR, 31.3-32.6) weeks in Type III (P < 0.01). The total intact survival rate was 100% for Type I, 77.3% for Type II and 75.0% for Type III (P < 0.001). Multivariate analysis demonstrated that early GA at diagnosis (odds ratio (OR), 0.83 (95% CI, 0.69-0.99); P = 0.04) and the presence of Type II or III vs Type I at the last examination (OR, 13.16 (95% CI, 1.53-113.32); P = 0.02) were associated with preterm birth < 32 weeks' gestation. Early GA at diagnosis was also associated with the composite adverse outcome (OR, 0.60 (95% CI, 0.36-0.99); P = 0.04).

CONCLUSIONS

The classification system of MCDA pregnancy complicated by sIUGR, according to the UA Doppler flow pattern of the IUGR twin at final examination, is associated with perinatal outcome. Importantly, the UA Doppler flow pattern can change during gestation, which has an impact on the risk of fetal death. Nevertheless, under strict fetal surveillance, the perinatal outcome of these pregnancies is favorable. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Twin to twin transfusion syndrome

Twin to twin transfusion syndrome (TTTS) is a common complication that typically presents in the second trimester of pregnancy in 10-15% of monochorionic twins due to net transfer of volume and hormonal substances from one twin to the other across vascular anastomoses on the placenta. Without recognition and treatment, TTTS is the greatest contributor to fetal loss prior to viability in 90-100% of advanced cases. Ultrasound diagnosis of monochorionicity is most reliable in the first trimester and sets the monitoring strategy for this type of twins. The diagnosis of TTTS is made by ultrasound with the findings of polyhydramnios due to volume overload and polyuria in one twin and oligohydramnios due to oliguria of the co-twin. Assessment of bladder filling as well as arterial and venous Doppler patterns are required for staging disease severity. Assessment of fetal cardiac function also provides additional insight into the fetal cardiovascular impacts of the disease as well as help identify fetuses that may require postnatal follow up. Fetoscopic laser ablation of the communicating vascular anastomoses between the twins is the standard treatment for TTTS. It aims to cure the condition by interrupting the link between their circulations and making them independent of one another. Contemporary outcome data after laser surgery suggests survival for both fetuses can be anticipated in up to 65% of cases and survival of a single fetus in up to 88% of cases. However, preterm birth remains a significant contributor to postnatal morbidity and mortality. Long term outcomes of TTTS survivors indicate that up to 11% of children may show signs of neurologic impairment. Strategies to minimize preterm birth after treatment and standardized reporting by laser centers are important considerations to improve overall outcomes and understand the long-term impacts of TTTS.

Feasibility of fetal left modified myocardial performance index in twin anemia polycythemia sequence and perinatal outcomes after antenatal intervention

OBJECTIVE

To evaluate the feasibility and clinical value of fetal left modified myocardial performance index (Mod-MPI) in assessment and management of prenatal twin anemia polycythemia sequence (TAPS).

METHODS

We retrospectively reviewed fetuses with TAPS diagnosed prenatally between 2015 and 2019 at Asan Medical Center. Doppler ultrasound evaluation including the peak systolic velocity (PSV) of the middle cerebral artery (MCA) and fetal echocardiography including left Mod-MPI were evaluated and followed up after antenatal management.

RESULTS

Among 10 cases of fetal twin pregnancies with prenatal TAPS, six were spontaneous and four were post-laser TAPS. Left Mod-MPI was abnormal in one or both twins of nine cases (90%) including all post-laser TAPS (n = 4) and 83.3% of spontaneous TAPS (n = 5). Three recipients, one donor and three former recipients/new donors had elevated left Mod-MPI values, and one donor, one recipient, two former donors/new recipients had decreased values. Antenatal intervention was performed in eight cases with intrauterine transfusion (n = 4), fetoscopic laser surgery (n = 2), radiofrequency ablation (n = 1), and intrauterine transfusion followed by radiofrequency ablation (n = 1). The remaining two cases were either delivered or managed expectantly. MCA-PSV and left Mod-MPI became normal on the follow-up scans in all cases except the delivered case. There were four fetal deaths: two occurred spontaneously and two were selectively terminated by radiofrequency ablation. Overall perinatal survival per fetus was 80% (16/20) and the median gestational age at delivery was 34.4 (range, 29.2-37.4) weeks. Neither postnatal death nor neurodevelopmental delay occurred during a median follow-up of 13 months (range, 0.25-60 months).

CONCLUSION

Fetal left Mod-MPI was useful for assessment of compromised fetal cardiac function in cases with prenatal TAPS. Application of fetal left Mod-MPI in prenatal staging of TAPS might help evaluate the severity of TAPS and decide timely antenatal intervention.

Fetal Growth Restriction: ACOG Practice Bulletin, Number 227

Fetal growth restriction, also known as intrauterine growth restriction, is a common complication of pregnancy that has been associated with a variety of adverse perinatal outcomes. There is a lack of consensus regarding terminology, etiology, and diagnostic criteria for fetal growth restriction, with uncertainty surrounding the optimal management and timing of delivery for the growth-restricted fetus. An additional challenge is the difficulty in differentiating between the fetus that is constitutionally small and fulfilling its growth potential and the small fetus that is not fulfilling its growth potential because of an underlying pathologic condition. The purpose of this document is to review the topic of fetal growth restriction with a focus on terminology, etiology, diagnostic and surveillance tools, and guidance for management and timing of delivery.

Acardiac twin pregnancies part VI: Why does acardiac twinning occur only in the first trimester?

BACKGROUND

Clinical observation suggests that acardiac twinning occurs only in the first trimester. In part, this contradicts our previous analysis (part IV) of Benirschke's concept that unequal embryonic splitting causes unequal embryo/fetal blood volumes and pressures. Our aim is to explain why acardiac onset is restricted to the first trimester.

METHODS

We applied the vascular resistance scheme of two fetuses connected by arterio-arterial (AA) and veno-venous (VV) anastomoses, the small VV resistance approximated as zero. The smaller twin has volume fraction α < 1 of the assumed normal larger twin, and has only access to fraction X < 1 of its placenta; the larger twin's larger mean arterial pressure accesses the remaining fraction. Before 13 weeks, embryos have a much smaller vascular resistance than placentas. After 13 weeks, when maternal blood provides oxygen, smaller twins can increase their vascular volume by hypoxemia-mediated neovascularization. Estimated AA radii at 40 weeks, r_AA (40), are 0.5-1.3 mm.

RESULTS

Embryos with α < 0.33 unlikely survive 13 weeks and acardiac twinning occurs under appropriate conditions (AA-VV, small placenta). Acardiac body perfusion occurs because of a much smaller vascular resistance than the placenta. When α > 0.33 and r_AA (40)=1.3 mm, modeled survival is >32 weeks.

CONCLUSION

Before 13 weeks, embryos with α < 0.33 cannot survive and may result in the onset of acardia. Beyond 13 weeks, fetuses with α ≥ 0.33 survive because r_AA (40) is too small for acardiac onset. Following fetal demise, exsanguination from the live twin increases its blood volume and, we assumed also, its vascular resistance. Perfusion then occurs through the lower resistance placenta.

Inter-twin differences in fetal echocardiographic findings are associated with decreased dual twin survival in twin-twin transfusion syndrome

OBJECTIVE

To determine if inter-twin differences in fetal echocardiographic findings are associated with fetal survival in monochorionic pregnancies complicated by twin-to-twin transfusion syndrome (TTTS).

METHODS

This study included women who underwent laser surgery for TTTS between 2012 and 2018 at a single institution. Echocardiographic cardiac parameters in the donor and recipient twins were compared using Z-scores and regression analyses (adjusted for confounding variables) to determine whether any measurable inter-twin differences were associated with neonatal survival at birth. Results are expressed as (Odds ratio [95% confidence interval], p-value).

RESULTS

Fetal echocardiography and delivery information was available in 124 TTTS cases. Dual live-birth occurred in 72% and at least one live-birth was seen in 89% of cases. Sixty-four percent (51/79) of recipient twins had evidence of cardiac dysfunction compared to 10% (8/79) of the donor twins (p < .01). In the logistic regression, inter-twin differences in left ventricle short axis dimension (0.62[0.44-0.87], p < .01), aortic valve diameter (0.67[0.45-0.99], p = .047), peak systolic velocity across the pulmonary artery (PA-PSV) (0.09[0.01-0.53], p < .01) and mitral valve diameter (0.56[0.38-0.84], p < .01) were associated with lower dual twin survival at birth.

CONCLUSION

Inter-twin differences in left cardiac geometry and function are associated with decreased survival at delivery in TTTS.

Maternal vascular endothelial growth factor receptor and interleukin levels in pregnant women with twin-twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) is an unusual and serious condition that occurs in twin pregnancies when identical twins share a placenta but develop discordant amniotic fluid volumes. TTTS is associated with an increased risk of fetal death and birth defects if untreated. This study investigated the soluble levels of biomarkers including growth factors and interleukins in pregnant women with and without TTTS during pregnancy. We quantified plasma levels of VEGF-R1, VEGF-R2, IL-1β, IL-6 and IL-8 in twin pregnant women with (n=53) and without TTTS (n=72) and in women with single pregnancy (n=30) by ELISA and analyzed the association of maternal circulating biomarker levels with TTTS. Our results showed that maternal VEGF-R1 levels were significantly higher in twins compared to single pregnancy (P<0.05) and were decreased in the second trimester compared to the first trimester (P = 0.065, 0.019 and 0.072 for twins with and without TTTS and single pregnancy, respectively). VEGF-R2 levels had a trend to be lower in twins compared to single pregnancy. In addition, soluble VEGF-R1 and VEGF-R2 levels were significantly decreased while IL-6 levels were increased after surgical treatment with laser in twin pregnant women with TTTS (P = 0.016, 0.041 and 0.04, respectively). These results suggest that IL-6, VEGF-R1 and VEGF-R2 are involved in vascular regulation and stabilization in twin pregnancies and may contribute to the pathogenesis of TTTS and thus play a prognostic role in the surgical treatment of TTTS.

Monochorionic twins after in-vitro fertilization: do they have poorer outcomes?

OBJECTIVE

To compare the outcome of monochorionic diamniotic (MCDA) twin pregnancies conceived by in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) with that of spontaneously conceived MCDA twins.

METHODS

This was a retrospective cohort study of MCDA twin pregnancies conceived after IVF/ICSI or spontaneously, followed from the first trimester onwards at a single center between January 2002 and September 2018. The primary outcome was survival per fetus from the first trimester until 28 days after birth. Secondary outcome measures were number of survivors, miscarriage, termination of pregnancy, intrauterine and neonatal death, major congenital anomalies, twin-twin transfusion syndrome, selective fetal growth restriction, gestational age at birth, delivery before 32 weeks' gestation, mode of delivery, admission to the neonatal intensive care unit, birth weight and birth-weight discordance.

RESULTS

Of the 654 MCDA pregnancies included in the analysis, 80 were conceived by IVF/ICSI and 574 spontaneously. Overall fetal and neonatal survival was significantly lower in the IVF/ICSI group than in the spontaneous-conception group (79% vs 90%; P = 0.001). In the IVF/ICSI group, compared with the spontaneous-conception group, loss of one or both twins occurred twice as often (29% vs 14%; P = 0.001) and there was a higher risk of second-trimester miscarriage (8% vs 1%; P = 0.002).

CONCLUSIONS

MCDA twins conceived after IVF/ICSI have lower overall survival rates and higher rates of second-trimester miscarriage than do spontaneously conceived MCDA twins. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Placental Anatomy and Function in Twin Gestations

With an increasing incidence of twin gestations, understanding the inherent risks associated with these pregnancies is essential in modern obstetrics. The unique differences in placentation in twins contribute to the increased risks. Monochorionic twins are susceptible to complications because of their unique placental architecture, including twin-to-twin transfusion syndrome, the twin anemia-polycythemia sequence, selective intrauterine growth restriction, and the twin reversed arterial perfusion sequence. Knowing the clinical correlations of placental anatomy in these gestations helps perinatal pathologists perform a more informed placental evaluation, allowing for better care for the mother and her children.

Uncomplicated Monochorionic Twins: Two Normal Hearts Sharing One Placenta

Cardiovascular dysfunction has been reported in complicated monochorionic diamniotic (MCDA) pregnancies; however, little is known whether hemodynamic changes occur in uncomplicated MCDA twins. A prospective observational study was conducted including 100 uncomplicated MCDA twins matched by gestational age to 200 low-risk singletons. Echocardiography was performed at 26-30 weeks gestation and cord blood B-type natriuretic peptide (BNP) was measured at delivery. In both groups, z-scores for echocardiographic parameters were within normal ranges; however the monochorionic group had larger atrial areas (mean (standard deviation) right atria-to-heart ratio: 17.0 (2) vs. 15.9 (1); p = 0.018; left atria-to-heart ratio: 17.0 (3) vs. 15.8 (2); p < 0.001) and signs of concentric hypertrophy (right relative wall thickness: 0.66 (0.12) vs. 0.56 (0.11); p < 0.001; left relative wall thickness: 0.69 (0.14) vs. 0.58 (0.12); p < 0.001). Longitudinal function was increased in twins, leading to higher tricuspid annular plane systolic excursion (6.9 mm (0.9) vs. 5.9 mm (0.7); p < 0.001) and mitral annular plane systolic excursion (4.9 mm (0.8) vs. 4.4 mm (1.1); p < 0.001. BNP levels at birth were also higher in MCDA twins (median [interquartile range]: 20.81 pg/mL [16.69-34.01] vs. 13.14 pg/mL [9.17-19.84]; p < 0.001). Thus, uncomplicated MCDA fetuses have normal cardiac shape and function, but signs of cardiac adaptation were identified by echocardiographic and biochemical parameters, when compared with singletons.

Fetal ventricular strain in uncomplicated and selective growth-restricted monochorionic diamniotic twin pregnancies and cardiovascular response in pre-twin-twin transfusion syndrome

OBJECTIVES

Our primary aim was to confirm whether intertwin discordance in ventricular strain and ductus venosus (DV) time intervals predicts twin-twin transfusion syndrome (TTTS). Secondary aims were to create gestational-age ranges for ventricular strain in uncomplicated monochorionic diamniotic (MCDA) twin pregnancies without selective intrauterine growth restriction (sIUGR) and to characterize the relationship of ventricular strain with gestational age in MCDA twin pregnancies with sIUGR that did not develop TTTS.

METHODS

In the period 2015-2018, we enrolled 150 MCDA twin pregnancies consecutively into this prospective, blinded study of global longitudinal left and right ventricular strain. With the observer blinded to twin pairing and pregnancy outcome, videoclips of the four-chamber view, which had been recorded during ultrasound surveillance in the usual window for development of TTTS (16-26 completed gestational weeks), underwent offline measurement of strain. Uncomplicated MCDA twin pregnancies, without sIUGR, were used to test the association between strain, gestational age and estimated fetal weight using mixed-effects multilevel regression. Inter-rater reliability was tested in 208 strain measurements in 31 fetuses from pregnancies which did not develop TTTS and within-fetus variation was assessed in 16 such fetuses, in which multiple four-chamber views were taken on the same day. The effect of sIUGR on strain in otherwise uncomplicated MCDA twin pregnancy was analyzed. MCDA twin pregnancies were defined as 'pre-TTTS' when, having been referred for TTTS evaluation, they did not satisfy Quintero staging criteria, but subsequently developed TTTS requiring laser treatment. MCDA pregnancies which did not develop TTTS comprised the 'non-TTTS' group. Cardiovascular parameters measured in these cases included tissue Doppler parameters and DV early filling time as a percentage of the cardiac cycle (DVeT%). Intertwin strain and DVeT% discordance was compared between non-TTTS and pre-TTTS cases, matched for gestational age.

RESULTS

Paired strain data were available for intertwin comparison in 127/150 MCDA twin pregnancies, comprising 14 pre-TTTS and 113 non-TTTS pregnancies, after exclusions. Scans were collected at a median frame rate of 97 (range, 28-220) Hz. Laser therapy was performed at a median gestational age of 20.6 (range, 17.2-26.6) weeks. There were no group differences in right (RV) or left (LV) ventricular strain discordance between 68/113 non-TTTS and 13/14 pre-TTTS MCDA twin pregnancies < 20 completed gestational weeks (RV, P = 0.338; LV, P = 0.932). DVeT% discordance > 3.6% was found in eight of 13 pre-TTTS pregnancies. In non-TTTS pregnancies, the estimated variability in ventricular strain within each twin during the day was high (RV, 19.7; LV, 12.9). However, within each pair (intertwin variation), variability was low (RV, 5.5; LV, 2.9). Interclass correlation reflecting the proportion of total variability represented by the variability between twin pairs was low (RV, 0.22; LV, 0.18). Both RV (P < 0.001) and LV (P = 0.025) strain showed a negative association with gestational age. Among non-TTTS MCDA twin pregnancies, LV strain was, on average, higher by 1.83 in sIUGR compared with normally grown fetuses (P = 0.023), with no statistically significant difference in RV strain (P = 0.271).

CONCLUSIONS

Although ventricular strain has been reported previously as a possible predictor of developing TTTS, in this blinded, prospective study, we found no significant intergroup differences in ventricular strain in pre-TTTS compared with age-matched non-TTTS MCDA twin pregnancies. We recommend using DVeT% discordance as a more practical screening tool in MCDA twin pregnancies. This study also provides new information on the changes with gestational age, and the biological and technical variation, of global longitudinal ventricular strain in uncomplicated MCDA twin pregnancies and those with isolated sIUGR. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Segmentation of the placenta and its vascular tree in Doppler ultrasound for fetal surgery planning

PURPOSE

Twin-to-twin transfusion syndrome (TTTS) is a serious condition that occurs in about 10-15% of monochorionic twin pregnancies. In most instances, the blood flow is unevenly distributed throughout the placenta anastomoses leading to the death of both fetuses if no surgical procedure is performed. Fetoscopic laser coagulation is the optimal therapy to considerably improve co-twin prognosis by clogging the abnormal anastomoses. Notwithstanding progress in recent years, TTTS surgery is highly risky. Computer-assisted planning of the intervention can thus improve the outcome.

METHODS

In this work, we implement a GPU-accelerated random walker (RW) algorithm to detect the placenta, both umbilical cord insertions and the placental vasculature from Doppler ultrasound (US). Placenta and background seeds are manually initialized in 10-20 slices (out of 245). Vessels are automatically initialized in the same slices by means of Otsu thresholding. The RW finds the boundaries of the placenta and reconstructs the vasculature.

RESULTS

We evaluate our semiautomatic method in 5 monochorionic and 24 singleton pregnancies. Although satisfactory performance is achieved on placenta segmentation (Dice ≥ 84.0%), some vascular connections are still neglected due to the presence of US reverberation artifacts (Dice ≥ 56.9%). We also compared inter-user variability and obtained Dice coefficients of ≥ 76.8% and ≥ 97.42% for placenta and vasculature, respectively. After a 3-min manual initialization, our GPU approach speeds the computation 10.6 times compared to the CPU.

CONCLUSIONS

Our semiautomatic method provides a near real-time user experience and requires short training without compromising the segmentation accuracy. A powerful approach is thus presented to rapidly plan the fetoscope insertion point ahead of TTTS surgery.