Maternal plasma angiotensin 1-7 concentration is related to twin pregnancy chorionicity in the third trimester of pregnancy

Introduction

Twin gestation is related to a higher risk of hypertensive disorders in pregnancy with possible risk stratification depending on chorionicity. It may be related to differences in plasma renin-angiotensin-aldosterone components between monochorionic and dichorionic twin pregnancies. The study aimed to analyze the plasma ANG II and ANG 1-7 concentrations in women with monochorionic and dichorionic twin gestation.

Methods

A prospective observational study included 79 women between 32 and 34 weeks of gestation with twin pregnancy (31 with monochorionic gestation and 48 with dichorionic gestation). Angiotensin II and angiotensin 1-7 concentrations were measured in the collected blood samples.

Results

No significant differences were observed in angiotensin II concentrations between the dichorionic and monochorionic group with significantly higher levels of angiotensin 1-7 being observed in the dichorionic group. Angiotensin 1-7 level was higher than angiotensin II in 20 women (64.5%) in the monochorionic group and in 42 women (87.5%, p=0.01) in the dichorionic group. Higher plasma concentrations of angiotensin II and lower concentrations of angiotensin 1-7 were found in 5 women with gestational hypertension and in 3 with preeclampsia compared to normotensive women.

Discussion

It is the first study investigating angiotensin II and angiotensin 1-7 in twin pregnancies regarding chorionicity. Our results showed that plasma angiotensin 1-7 concentration was related to chorionicity, while plasma angiotensin II level was not. In most women with twin gestation angiotensin 1-7 concentration exceeded the concentration of angiotensin II. A switch in the relation between angiotensin II and angiotensin 1-7 was observed in hypertensive pregnant women.

To be born twin: effects on long-term neurodevelopment of very preterm infants-a cohort study

Objective

To examine the effect of twin birth on long-term neurodevelopmental outcomes in a cohort of Italian preterm infants with very low birth weight.

Study design

We performed a retrospective cohort study on children born in a tertiary care centre. We included children born between 1 January 2007 and 31 December 2013 with a gestational age (GA) of ≤32 weeks and birth weight of <1,500 g. The infants born from twin pregnancies complicated by twin-to-twin transfusion syndrome and from higher-order multiple pregnancies were excluded. The children were evaluated both at 2 years corrected age and 5 years chronological age with Griffiths mental development scales revised (GMDS-R). The linear mixed effects models were used to study the effect of being a twin vs. being a singleton on GMDS-R scores, adjusting for GA, being born small for gestational age, sex, length of NICU stay, socio-economic status, and comorbidity score (CS) calculated as the sum of the weights associated with each of the major morbidities of the infants.

Results

A total of 301 children were included in the study, of which 189 (62.8%) were singletons and 112 (37.2%) were twins; 23 out of 112 twins were monochorionic (MC). No statistically significant differences were observed between twins and singletons in terms of mean general quotient and subscales at both 2 and 5 years. No effect of chorionicity was found when comparing scores of MC and dichorionic twins vs. singletons; however, after adjusting for the CS, the MC twins showed lower scores in the hearing and language and performance subscales at 5 years.

Conclusion

Overall, in our cohort of children born very preterm, twin infants were not at higher risk of neurodevelopmental impairment compared with singletons at pre-school age.

Pregnancy and perinatal outcomes of early vs late selective termination in dichorionic twin pregnancy: systematic review and meta-analysis

OBJECTIVE

To evaluate outcomes of dichorionic twin pregnancies undergoing early vs late selective termination of pregnancy (ST).

METHODS

MEDLINE, EMBASE, CINAHL and the Web of Science databases were searched electronically up to March 2022. The primary outcome of this study was pregnancy loss prior to 24 weeks' gestation. The secondary outcomes included preterm birth (PTB) before 37, 34, and 32 weeks, preterm prelabor rupture of membranes (PPROM), gestational age (GA) at delivery, Cesarean delivery, mean birth weight, 5-min Apgar score < 7, overall neonatal morbidity and neonatal survival. Only prospective or retrospective studies reporting data on the outcome of early (before 18 weeks) vs late (at or after 18 weeks) ST in dichorionic twin pregnancies were considered suitable for inclusion. Quality assessment of the included studies was performed using the Newcastle-Ottawa scale for cohort studies. Random-effects head-to-head meta-analysis was used to analyze the data.

RESULTS

Seven studies reporting on 649 dichorionic twin pregnancies were included in this systematic review. The risk of pregnancy loss prior to 24 weeks was significantly lower in dichorionic twin pregnancies undergoing early compared with late ST (1% vs 8%; odds ratio (OR), 0.25 (95% CI, 0.10-0.65); P = 0.004). The risk of PTB was significantly lower in dichorionic twin pregnancies undergoing early compared with late ST when considering PTB before 37 weeks (19% vs 45%; OR, 0.36 (95% CI, 0.23-0.57); P < 0.00001), before 34 weeks (4% vs 19%; OR, 0.24 (95% CI, 0.11-0.54); P = 0.0005) and before 32 weeks (4% vs 20%; OR, 0.21 (95% CI, 0.05-0.85); P = 0.03). The mean birth weight was significantly greater in the early-ST group (mean difference (MD), 392.2 g (95% CI, 59.1-726.7 g); P = 0.02), as was the mean GA at delivery (MD, 2.47 weeks (95% CI, 0.04-4.91 weeks); P = 0.049). There was no significant difference between dichorionic twin pregnancies undergoing early compared with late ST in terms of PPROM (P = 0.27), Cesarean delivery (P = 0.38), 5-min Apgar score < 7 (P = 0.35) and neonatal survival of the non-reduced twin (P = 0.54).

CONCLUSIONS

The risk of pregnancy loss prior to 24 weeks and the rate of PTB before 37, 34 and 32 weeks were significantly higher in dichorionic twin pregnancies undergoing late vs early ST, thus highlighting the importance of early diagnosis of fetal anomalies in twin pregnancies. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Molecular Characterization of a Rare Case of Monozygotic Dichorionic Diamniotic Twin Pregnancy after Single Blastocyst Transfer in Preimplantation Genetic Testing (PGT)

Preimplantation genetic testing (PGT) is widely used to select unaffected embryos, increasing the odds of having a healthy baby. During the last few decades, it was accepted that monozygotic dichorionic diamniotic twin pregnancies occurred from the embryo splitting before Day 3 postfertilization according to Corner’s dogma. Hence, the occurrence of a dichorionic diamniotic twin pregnancy after a single blastocyst transfer was considered a dizygotic pregnancy resulting from blastocyst transfer and concurrent natural fertilization. In our study, we have provided for the first time molecular proof that a single blastocyst transfer can result in a monozygotic dichorionic diamniotic twin pregnancy, invalidating Corner’s dogma. In this case, we recommend systematically assessing the genetic status of dichorionic twins after single blastocyst transfer using prenatal diagnosis to exclude the risk from a potential concurrent spontaneous pregnancy and to ensure that both fetuses are unaffected. To achieve this goal, we have developed here an innovative noninvasive prenatal diagnosis by exclusion of paternal variants with droplet digital PCR, maximizing the reliability of genetic diagnosis. Further multicentric prospective studies using genetic testing are now required to establish the rate of blastocyst splitting leading to dichorionic pregnancy in PGT and to identify the risk factors.

Intertwin membrane cord insertion in dichorionic twin pregnancy: The description and comparison with other umbilical cord insertion types

PURPOSE

Multiple pregnancy is associated with high perinatal mortality and morbidity. Abnormal cord insertions more common in twin pregnancies compared to singleton pregnancies and velamentous cord insertion is related with poor pregnancy outcomes. There is no definition of velamentous cord insertion into the intertwine membrane between two fetuses in the literature.

METHODS

In our single-center cross-sectional study, monochorionic-diamniotic and dichorionic-diamniotic twins who were admitted to our clinic between 18 + 0 and 23 + 6 weeks of pregnancy were enrolled in this study. We evaluated fetal, placental, and umbilical cord abnormalities in addition to fetal growth restrictions and weight discordance by ultrasonography.

RESULTS

Although abnormal cord insertion frequency was significantly higher in monochorionic twins (p = 0.003), intertwin membrane cord insertion could only occur in dichorionic twins. In cases with cord insertion anomaly; FGR and weight discordance was observed more frequently (p < 0.001 and p = 0.003, respectively). Weight discordance, the presence of abnormal cord insertion and abnormal UAD were found as statistically significant predictors of FGR (p < 0.001, p = 0.021, and p < 0.001, respectively).

CONCLUSION

Intertwin membrane insertion is a novel umbilical cord insertion abnormality. The presence of abnormal umbilical cord insertion is a risk factor for poor pregnancy outcomes in twin pregnancies.

Perinatal outcomes of fetoscopic laser surgery for twin-twin transfusion syndrome in triplet pregnancy: cohort study, systematic review and meta-analysis

OBJECTIVES

The aims of this study were to investigate the perinatal outcome of dichorionic triamniotic (DCTA) and monochorionic triamniotic (MCTA) triplet pregnancies complicated by twin-twin transfusion syndrome (TTTS) treated with fetoscopic laser photocoagulation (FLP) in two academic fetal centers, and to conduct a systematic review of previously published data to investigate perinatal survival in this targeted population.

METHODS

The first part of the study was a retrospective cohort study of prospectively collected data of consecutive triplet pregnancies with TTTS that underwent FLP at two fetal treatment centers between 2012 and 2020. Demographic, preoperative and operative variables and postoperative outcome were collected. Perinatal outcomes were investigated. The second part of the study was a systematic review and meta-analysis of studies evaluating the outcome of DCTA and/or MCTA triplet pregnancies, including our cohort study. PubMed, Web of Science and Scopus were searched from inception to September 2020. Primary outcomes were fetal survival (survival to birth), neonatal survival (survival to 28 days of age) and gestational age (GA) at birth.

RESULTS

A total of 31 sets of triplets with TTTS managed with FLP were included in the cohort study. Of these, 24 were DCTA and seven were MCTA. There were no significant differences in preoperative and operative variables between the two groups. There were also no significant differences between groups in GA at delivery or perinatal survival rate, including fetal and neonatal survival of at least one triplet, at least two triplets and all three triplets. Nine studies, including our cohort study, were included in the systematic review (156 DCTA and 37 MCTA triplet pregnancies treated with FLP). The overall fetal and neonatal survival was 79% (95% CI, 75-83%) and 75% (95% CI, 71-79%), respectively, in DCTA cases and 74% (95% CI, 52-92%) and 71% (95% CI, 49-89%), respectively, in MCTA cases. The rate of preterm birth before 28 weeks and before 32 weeks' gestation was 14% (95% CI, 4-29%) and 61% (95% CI, 50-72%), respectively, in DCTA triplets and 21% (95% CI, 3-45%) and 82% (95% CI, 62-96%), respectively, in MCTA triplets.

CONCLUSIONS

Triplet pregnancies with TTTS are at high risk of adverse perinatal outcome and preterm birth, regardless of chorionicity. The rate of survival after FLP in MCTA triplets was higher in our study than that reported in previous studies and is currently comparable with survival in DCTA triplets, which could be due to improved surgical skills. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Association between Respiratory Distress Syndrome of Newborns and Fetal Growth Restriction Evaluated Using a Dichorionic Twin Pregnancy Model

AIMS

To evaluate the association between respiratory distress syndrome (RDS) and intrauterine fetal growth restriction (IUGR) by using a dichorionic twin model.

METHODS

We retrospectively analyzed twins delivered between September 2012 and December 2018. A dichorionic (DC) twin pregnancy with selective IUGR (sIUGR) was defined as the presence of (i) a birthweight discordance of ≥25% and (ii) a smaller twin with birth weight below the 10th percentile. Pregnancies with major fetal anomalies, delivery at gestational age below 23 weeks, and intrauterine fetal demise were excluded.

RESULTS

We included 53 DC twins with sIUGR. The sIUGR twin had a higher risk of RDS than did his appropriate for gestational age (AGA) cotwin (32.1% vs. 11.3%, p = 0.001); however, the risk of severe RDS did not significantly differ between the twins (17.0% vs 9.4%, p = 0.125). The findings of logistic regression analysis indicated that younger gestational age (weeks) at delivery (odds ratio = 0.48, p < 0.001) and IUGR (odds ratio = 13.87, p = 0.009) were significant risk factors for RDS in newborns in DC twin pregnancies with selective sIUGR.

CONCLUSIONS

IUGR was identified as a risk factor for newborn RDS. However, the association between IUGR and severe newborn RDS was not significant possibly due to the small sample size of this study.

Epidemiology, Genetics and Epigenetics of Congenital Heart Diseases in Twins

Congenital heart defects (CHDs) refer to abnormalities in the heart function that arise at the fetal stages. It is the most common birth defect that affects 0.8% of all liveborn infants. There is an increase in the incidence of congenital heart disease in monochorionic twin gestation. A six-fold increase in CHDs exists among monochorionic twins especially in association with twin-twin transfusion syndrome (TTTS) compared to dichorionic twin pregnancy. In this review article, we discussed the epidemiology, the role of genetics like protein-coding genes, epigenetics, placenta, hemodynamics and environmental factors in the etiology of CHD in twins.

We conducted a literature search in PubMed indexed journals using the medical terms "twin pregnancy" and "congenital heart defect" to provide an overview of the uptrend in CHD in twin pregnancies, primarily due to assisted reproductive technologies (ARTs) and multiple other factors. Both the heart and placenta are vascular and share a common development window; therefore, CHD can develop secondary to placental pathologies. Among environmental factors, the strongest association of maternal smoking with CHD has been seen. We studied the causative factors to suggest improvement in echocardiographic skills in case of abnormal findings in twin gestations to decrease the CHD-associated morbidity and mortality, as early diagnosis allows doctors to precisely determine the risk of CHD. Systemic ultrasound scanning with five transverse views is very effective in diagnosing fetal CHD in twin pregnancy. In the case of genetics, prenatal counseling allows the expectant to understand the full ramifications of possible events after the pregnancy. The pathological basis of malformations specific to conjoined twinning and twin reversed arterial perfusion sequence is addressed. Also, there is evidence that folate supplementation may be protective against CHD but more research is needed to clarify the mechanisms.

We concluded from the literature that monochorionic twins are at high risk of CHD. Chorionicity seems to play a more vital role than zygosity. Even the type of heart defect in monochorial twin pregnancies was unique from single, dizygotic, or dichorionic twin pregnancies. We also emphasize improving echocardiographic skills of technicians in referring ART dichorionic twin fetuses with suspicious findings to fetal cardiologists and performing postnatal scans in the case of TTTS. To understand the role of the placenta, making use of newer technologies and examining the placenta both during pregnancy and beyond delivery will play a vital role in understanding the etiology. Even identifying early signals impacting the heart and placental vasculature and correcting them using advanced technology could downtrend the incidence in coming years. Increased maternal age as well as multiple pregnancies increasing the risk of CHD has also been implicated. For more clarity on the role of genetics, the cost of DNA sequencing needs to decrease. This will enable whole-genome sequencing in the future thus helping to discover the gene responsible for CHD ultimately proving beneficial for future generations. For environmental factors, we have to rely on observational studies to assess the risk to the unborn child. There is difficulty in studying natural factors due to the unreliability of exposure to contaminants like pesticides and air pollution.

Twin anemia polycythemia sequence in dichorionic diamniotic twins: A case report and review of the literature

Although rare, literature demonstrates evidence that vascular anastomoses do occur in dichorionic twins. Therefore, twin anemia polycythemia sequence should be considered as a differential diagnoses in dichorionic twins if there is suspicion on antenatal ultrasound.

Monozygotic dichorionic-diamniotic twin pregnancy after single embryo transfer at blastocyst stage: a case report

Single embryo transfer is highly encouraged on in vitro fertilization due to its lower rates of multiple pregnancy. Nevertheless, the likelihood of multiple pregnancy is higher when using assisted reproductive technology, probably because of embryo handling. Timing is crucial in the post-fertilization division of a single embryo to establish the amniocity and chorionicity of the gestation. In the case reported a 38 year-old woman, nulligravid, had a single blastocyst implanted, which resulted in monozygotic dichorionic-diamniotic twins. Despite being rare, there are reports of similar cases questioning the current knowledge on time of embryo division and the impact of assisted reproduction.

Cause of intrauterine and neonatal death in twin pregnancies (CoDiT): development of a novel classification system

OBJECTIVE

Twin pregnancies have a significantly higher perinatal mortality than singleton pregnancies. Current classification systems for perinatal death lack twin-specific categories, potentially leading to loss of important information regarding cause of death. We introduce and test a classification system designed to assign a cause of death in twin pregnancies (CoDiT).

DESIGN

Retrospective cross-sectional study.

SETTING

Tertiary maternity unit in England with a perinatal pathology service.

POPULATION

Twin pregnancies in the West Midlands affected by fetal or neonatal demise of one or both twins between 1 January 2005 and 31 December 2016 in which postmortem examination was undertaken.

METHODS

A multidisciplinary panel designed CoDiT by adapting the most appropriate elements of singleton classification systems. The system was tested by assigning cause of death in 265 fetal and neonatal deaths from 144 twin pregnancies. Cause of death was validated by another obstetrician blinded to the original classification.

MAIN OUTCOME MEASURES

Inter-rater, intra-rater, inter-disciplinary agreement and cause of death.

RESULTS

Cohen's Kappa demonstrated 'strong' (>0.8) inter-rater, intra-rater and inter-disciplinary agreement (95% CI 0.70-0.91). The commonest cause of death irrespective of chorionicity was the placenta; twin-to-twin transfusion syndrome (TTTS) was the commonest placental cause in monochorionic twins and acute chorioamnionitis in dichorionic twins.

CONCLUSIONS

This novel classification system records causes of death in twin pregnancies from postmortem reports with high inter-user agreement. We highlight differences in aetiology of death between monochorionic and dichorionic twins.

TWEETABLE ABSTRACT

New classification system for #twin cause of death 'CoDiT' shows high rater agreement.

Effect of delayed interval delivery of remaining fetus(es) in multiple pregnancies on survival: a systematic review and meta-analysis

BACKGROUND

The management of the pregnancy after delivery of the first fetus during a second-trimester miscarriage or very early preterm birth has not been well defined.

OBJECTIVE

The objective of the study was to evaluate whether delayed interval delivery of the remaining fetus(es) in twins/triplets is associated with improved survival, when compared with immediate delivery, after miscarriage or very preterm birth of the first fetus in multiple pregnancy.

DATA SOURCES

PubMed, MEDLINE, and Cochrane Library were systematically searched through January 2019. STUDY ELIGIBILITY CRITERIA (STUDY DESIGN, POPULATIONS, AND INTERVENTIONS): The following eligibility criteria applied: full-text original article; included at least 5 cases of delayed interval delivery for remaining fetus(es); and reported the survival rate of the first-born and the remaining fetus(es).

STUDY APPRAISAL AND SYNTHESIS METHODS

K.W.C. and W.W. searched, screened, and reviewed the articles. The quality of the studies was assessed according to the Strengthening the Reporting of Observational studies in Epidemiology checklist. If possible, data were stratified for assigned chorionicity. Effect sizes were pooled through a meta-analysis.

RESULTS

A total of 2295 published article and abstracts were identified. Only 16 studies met inclusion criteria. Meta-analysis of 492 pregnancies (432 twins [88%], 56 triplets [11%], 3 quadruplets and 1 quintuplets) showed that delayed interval delivery significantly improved the perinatal survival of remaining fetus(es) compared with the first born (odds ratio, 5.22, 95% confidence interval, 2.95-9.25, I² = 53%), before 20+0 weeks (odds ratio, 6.32, 95% confidence interval, 1.99-20.13, I² = 0%), between 20+0 and 23+6 weeks (odds ratio, 3.31, 95% confidence interval, 1.95-5.63, I² = 0%), and after 24+0 weeks (odds ratio, 1.92, 95% confidence interval, 1.21-3.05, I² = 0%), in dichorionic twin pregnancy (odds ratio, 14.89, 95% confidence interval, 6.19-35.84, I² = 0%), and unselected triplet pregnancy (odds ratio, 2.33, 95% confidence interval, 1.02-5.32, I² = 0%. ). Among the survivors, there were no significant differences in the short-term and long-term neonatal morbidities between the first-born and the remaining fetus(es). Serious maternal morbidity was reported in 39% of pregnancy after delayed interval delivery (71 of 183). In addition, 2 cases were managed by postpartum hysterectomy and 1 reported postoperative uterovaginal fistula. There were no recorded cases of maternal mortality.

CONCLUSION

Delayed interval delivery when a fetus has delivered in a multiple pregnancy is an effective management option to increase the survival rate of the remaining fetus(es). About 39% of women may experience morbidity following this management option.

Discordance for Potter's Syndrome in a Dichorionic Diamniotic Twin Pregnancy-An Unusual Case Report

INTRODUCTION

Potter's syndrome, also known as Potter's sequence, is an uncommon and fatal disorder. Potter's sequence in a multiple pregnancy is uncommon, and its frequency remains unknown. Worldwide in a diamniotic twin pregnancy, there are only a few cases described.

CASE REPORT

We present an unusual case discordance for Potter's syndrome in a dichorionic diamniotic twin pregnancy. Twin A had the typical physical and histological Potter's findings. Twin B had normal respiratory function and normal physical examination findings. There are many controversies about this condition in diamniotic twin pregnancy. One case report concluded that that the presence of a normal co-twin in diamniotic pregnancy prevented the cutaneous features seen in Potter's syndrome and ameliorated the pulmonary complications, whereas two other case studies reported that the affected twin had extrarenal features typical of the syndrome.

CONCLUSION

We performed an autopsy and calculated lung weight/body weight ratio to diagnose pulmonary hypoplasia. Histopathologic examination of lungs and kidneys was performed. We concluded that the appearance of extrarenal features in the affected twin depends on the amniocity.

Intrauterine growth discordance across gestation and birthweight discordance in dichorionic twins

BACKGROUND

Although intertwin size difference is an important measure of fetal growth, the appropriate cut point to define discordance is unclear. Few studies have assessed intertwin differences in estimated fetal weight longitudinally or in relation to size differences at birth.

OBJECTIVES

The objectives of the study were to estimate the magnitude of percentage differences in estimated fetal weight across gestation in dichorionic twins in relation to a fixed discordance cut point and compare classification of aberrant fetal growth by different measures (estimated fetal weight differences, birthweight discordance, small for gestational age).

STUDY DESIGN

Women aged 18-45 years from 8 US centers with dichorionic twin pregnancies at 8 weeks 0 days to 13 weeks 6 days gestation planning to deliver in participating hospitals were recruited into the Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies-Dichorionic Twins study and followed through delivery (n = 140; 2012-2013). Ultrasounds were conducted at 6 targeted study visits to obtain fetal biometrics and calculate estimated fetal weight. Percent estimated fetal weight and birthweight differences were calculated: ([weight_larger - weight_smaller]/weight_larger)*100; discordance was defined as ≥18% for illustration. Birth sizes for gestational age (both, 1, or neither small for gestational age) were determined; twins were categorized into combined birthweight plus small for gestational age groups: birthweight discordance ≥18% (yes, no) with both, 1, or neither small for gestational age. Linear mixed-models estimated percentiles of estimated fetal weight percent differences across gestation and compared estimated fetal weight differences between combined birthweight discordance and small for gestational age groups. A Fisher exact test compared birthweight discordance and small for gestational age classifications.

RESULTS

Median estimated fetal weight percentage difference increased across gestation (5.9% at 15.0, 8.4% at 38.0 weeks), with greater disparities at higher percentiles (eg, 90th percentile: 15.6% at 15.0, 26.3% at 38.0 weeks). As gestation advanced, an increasing percentage of pregnancies were classified as discordant using a fixed cut point: 10% at 27.0, 15% at 34.0, and 20% at 38.0 weeks. Birthweight discordance and small for gestational age classifications differed (P = .002); for birthweight discordance ≥18% vs <18%: 44% vs 71% had neither small for gestational age; 56% vs 18% had 1 small for gestational age; no cases (0%) vs 11% had both small for gestational age, respectively. Estimated fetal weight percent difference varied across gestation by birthweight discordance plus small for gestational age classification (P = .040). Estimated fetal weight percentage difference increased with birthweight discordance ≥18% (neither small for gestational age: 0.46%/week [95% confidence interval, 0.08-0.84]; 1 small for gestational age: 0.57%/week [95% confidence interval, 0.25-0.90]) but less so without birthweight discordance (neither small for gestational age: 0.17%/week [95% confidence interval, 0.06-0.28]; 1 small for gestational age: 0.03%/week [95% confidence interval, -0.17 to 0.24]); both small for gestational age: 0.10%/week [95% confidence interval, -0.15 to 0.36]).

CONCLUSION

The percentage of dichorionic pregnancies exceeding a fixed discordance cut point increased over gestation. A fixed cut point for defining twin discordance would identify an increasing percentage of twins as discordant as gestation advances. Small for gestational age and percentage weight differences assess distinct aspects of dichorionic twin growth. A percentile cut point may be more clinically useful for defining discordance, although further study is required to assess whether any specific percentile cut point correlates to adverse outcomes.

Associations between estimated foetal weight discordance and clinical characteristics within dichorionic twins: The NICHD Fetal Growth Studies

BACKGROUND

Birthweight discordance is well studied, with less known about longitudinal inter-twin differences in foetal growth.

OBJECTIVE

To examine inter-twin per cent differences in EFW (EFW_% ), head (HC_% ) and abdominal circumference (AC_% ), and femur length (FL_% ) across gestation in dichorionic twin gestations and explore associated characteristics.

METHODS

Foetal biometrics were assessed by ultrasound and EFW calculated at ≤6 study visits among women with dichorionic twin pregnancies enrolled in the NICHD Fetal Growth Studies cohort (US, 2012-2013). Inter-twin per cent difference was defined: ([Size_{larger twin}  - Size_{smaller twin} ]/Size_{larger twin}  × 100). Linear mixed models evaluated per cent differences in foetal biometrics at 15 weeks and their change per week overall and by maternal/neonatal characteristics in unadjusted and adjusted models.

RESULTS

In 140 pregnancies, inter-twin per cent differences increased across gestation for EFW (0.18%/week, 95% confidence interval [CI] 0.10, 0.27), HC (0.03%/week, 95% CI 0.00, 0.06), and AC (0.03%/week, 95%CI -0.01, 0.08) but decreased for FL (-0.03%/week, 95% CI -0.09, 0.02). After adjustment, change in EFW_% difference across gestation differed by pre-pregnancy body mass index (BMI [kg/m² ]; underweight [<18.5]; normal weight [18.5-24.9]; overweight [25.0-29.9]; obese [≥30.0]; P_interaction  = .022); and conception method (in vitro fertilisation [IVF], intrauterine insemination, ovulation induction medication, donor egg/embryo, none; P_interaction  = .060). While EFW_% difference increased with normal pre-pregnancy BMI (0.24%/week, 95% CI 0.12, 0.37), little change was noted with pre-pregnancy obesity (0.01%/week, 95% CI -0.15, 0.17). EFW_% difference increased in conceptions without fertility treatments (0.23%/week, 95% CI 0.11, 0.34) but not IVF conceptions (-0.00%/week, 95% CI -0.16, 0.16). Similar patterns of differences across gestation were noted for HC_% by conception method (P_interaction  = .026) and AC_% by pre-pregnancy BMI (P_interaction  = .071); changes in HC_% differed by parity (nulliparous, multiparous; P_interaction  = .004).

CONCLUSIONS

EFW_% difference increased across gestation in dichorionic twins, but remained stable with pre-pregnancy obesity or IVF conception, patterns mirrored for HC and AC. Research is needed to understand pathologic versus physiologic differential twin growth trajectories.

Proposal of the concept of mobility

Objectives: To identify if there is a specific neonatal morbidity/mortality among second twins relative to first twins.Study design: A 17-year (2001-2017) population-based observational cohort of all twin newborns born in the South of Reunion island after 21 weeks.Results: Among 1062 dichorionic (DTP) and 281 monochorionic twin pregnancies (2686 newborns), twin 2 have a doubled risk to be in breech presentation and a bad Apgar at 1 mn (≤6) in vaginal deliveries. Specific to dichorionic pregnancies, twin 2 were lighter by 50-60 g than twin 1, had higher rates of intrauterine growth retardation (IUGR), OR 1.33, p = .007, a doubled risk to have congenital abnormalities OR 2.1, p = .006.Conclusion: In dichorionic twin pregnancies, second twins having a doubled prevalence of severe congenital abnormalities are not completely elucidated and deserves further research. (1) We propose that twin 2 presenting higher risks of being IUGR and much higher risks of severe malformations suggest that during pregnancy, the less mobile of the two twins is "relegated" to the back of the uterus. (2) For interventions in the delivery room, systematically the most experimented neonatologist should plan to manage the second twin because significantly twin 2 presents higher problems than twin 1.

Ultrasound surveillance in twin pregnancy: An update for practitioners

Ultrasound has revolutionised the management of multiple pregnancies and their complications. Increasing frequency of twin pregnancies mandates familiarity of all clinicians with the relevant pathologies and evidence-based surveillance and management protocols for their care. In this review, we summarise the latest evidence relating to ultrasound surveillance of twin pregnancies including first trimester assessment and screening, growth surveillance and the detection and management of the complications of monochorionic pregnancies including twin-to-twin-transfusion syndrome, selective fetal growth restriction, twin reversed arterial perfusion sequence and conjoined twinning.

Placental Histopathology Differences and Neonatal Outcome in Dichorionic-Diamniotic as Compared to Monochorionic-Diamniotic Twin Pregnancies

OBJECTIVE

We aimed to compare the differences in placental histopathology lesions and pregnancy outcome in dichorionic-diamniotic (DCDA) versus uncomplicated monochorionic-diamniotic (MCDA) twin gestations.

STUDY DESIGN

Maternal characteristics, neonatal outcome, and placental histopathology reports of all twin deliveries between 24 and 41 weeks were reviewed. Excluded were pregnancies complicated by twin-to-twin transfusion syndrome, twin anemia-polycythemia sequence, selective intrauterine growth restriction, placenta previa, intrauterine fetal death, and malformation. Placental lesions were classified to maternal/fetal vascular malperfusion lesions. Umbilical cord abnormalities included hypo-/hypercoiling and abnormal insertion. Composite adverse neonatal outcome was defined as 1 or more early complications. Small for gestational age (SGA) was defined as birth weight ≤10th percentile.

RESULTS

The DCDA group (n = 362) was characterized by higher rates of assisted reproductive techniques ( P < .001) and nulliparity ( P = .03) as compared to the MCDA group (n = 65). Gestational age at delivery was similar between groups. Placental maternal vascular malperfusion lesions were more common in placentas from DCDA group (38.2% vs 23.1%; P = .016), while fetal vascular malperfusion lesions and abnormal cord insertion were more common in placentas from MCDA group ( P = .027; P< .001). The SGA and composite adverse neonatal outcome were more common in the MCDA group ( P = .031 and P = .038, respectively). By multivariate regression analysis, composite adverse neonatal outcome was found to be independently associated with the MCDA group, adjusted odds ratio (aOR) = 1.2, 95% confidence interval (CI) = 1.04 to 1.89, P = .041, and with placental fetal malperfusion lesions aOR = 1.3, 95% CI = 1.1 to 2.09, P = .038.

CONCLUSION

Placental pathology differs between MCDA and DCDA twin pregnancies. Adverse neonatal outcome in uncomplicated MCDA twins, as compared to DCDA twins, could be related to increased placental fetal malperfusion lesions and abnormal cord insertion.

Delayed-interval delivery can save the second twin: evidence from a systematic review

BACKGROUND

In case of preterm birth in twins, it is not well established if the second twin benefits from a delayed-interval delivery.

OBJECTIVE

The main objective of this systematic review is to evaluate survival benefit of the second twin from delayed interval delivery compared to the first twin. Secondly, we will evaluate the survival benefit of the procedure when performed equal to or after 24 weeks gestational age of the first born.

METHODS

Delayed interval delivery was defined as every attempt to perform a delayed interval delivery with at minimum placement of a high ligature of the umbilical cord and a delay of delivery of at least 24 hours. Based on the PRISMA method, a systematic review was performed. Controlled and observational studies reporting at least 3 cases of delayed interval delivery in dichorionic diamniotic twin pregnancy describing the outcome of the first and the second twin were included. Case reports and papers on triplet or higher order pregnancies were excluded. Primary data included gestational age and outcome of the first and second born. Metadata concern management strategies (tocolysis, antibiotics, cerclage), neonatal data (sex, birth weight and morbidity) and maternal complications. The methodological quality of included studies was assessed using the "IHE quality appraisal checklist for assessing the quality of case series". Meta-analysis was performed by computing relative risk (RR) with its 95% confidence interval (CI) using the random-effects model. Statistical heterogeneity was tested using the I² and Chi² statistics. Since there is no control group for the secondary outcomes, these are presented by narrative synthesis.

RESULTS

Mortality data were extracted from 13 articles, reporting a total of 128 cases of delayed interval delivery. In the analysis, the second born had a significantly lower mortality risk compared to the first born (relative risk = 0.44, 95% confidence interval = 0.34 - 0.57, P<0.0001, I²= 0%, P=0.70). For the analysis of mortality of the second born foetus versus the first born when the first delivery was at ≥24 weeks of gestational age, 12 articles were included. In the analysis 4 reports were excluded since there were no events (no mortality) in both groups (first and second born) making analysis impossible. For the 36 cases included, the second born had a significantly lower mortality risk compared to the first born if delivery of the first born occurred at ≥ 24 weeks gestational age (relative risk=0.37, 95% confidence interval= 0.17 - 0.82, P=0.014, I²=0%, P=0.82).

CONCLUSIONS AND IMPLICATIONS

In carefully selected twin pregnancies the survival of the second born twin may improve with delayed interval delivery, also if the first was born at or after 24 weeks. Management protocols in the studies included vary, making it difficult to propose a uniform strategy for delayed interval delivery. Families must be informed about the possibility that a nonviable infant would survive to a periviable gestational age with a risk of severe sequels after birth as well as the possibility of maternal complications.

Dichorionic twin trajectories: the NICHD Fetal Growth Studies

BACKGROUND

Systematic evaluation and estimation of growth trajectories in twins require ultrasound measurements across gestation that are performed in controlled clinical settings. Currently, there are few such data for contemporary populations. There is also controversy about whether twin fetal growth should be evaluated with the use of the same benchmarks as singleton growth.

OBJECTIVES

Our objective was to define the trajectory of fetal growth in dichorionic twins empirically using longitudinal 2-dimensional ultrasonography and to compare the fetal growth trajectories for dichorionic twins with those based on a growth standard that was developed by our group for singletons.

STUDY DESIGN

A prospective cohort of 171 women with twin gestations was recruited from 8 US sites from 2012-2013. After an initial sonogram at 11 weeks 0 days-13 weeks 6 days of gestation during which dichorionicity was confirmed, women were assigned randomly to 1 of 2 serial ultrasonography schedules. Growth curves and percentiles were estimated with the use of linear mixed models with cubic splines. Percentiles were compared statistically at each gestational week between the twins and 1731 singletons, after adjustment for maternal age, race/ethnicity, height, weight, parity, employment, marital status, insurance, income, education, and infant sex. Linear mixed models were used to test for overall differences between the twin and singleton trajectories with the use of likelihood ratio tests of interaction terms between spline mean structure terms and twin-singleton indicator variables. Singleton standards were weighted to correspond to the distribution of maternal race in twins. For those ultrasound measurements in which there were significant global tests for differences between twins and singletons, we tested for week-specific differences using Wald tests that were computed at each gestational age. In a separate analysis, we evaluated the degree of reclassification in small for gestational age, which was defined as <10th percentile that would be introduced if fetal growth estimation for twins was based on an unweighted singleton standard.

RESULTS

Women underwent a median of 5 ultrasound scans. The 50th percentile abdominal circumference and estimated fetal weight trajectories of twin fetuses diverged significantly beginning at 32 weeks of gestation; biparietal diameter in twins was smaller from 34-36 weeks of gestation. There were no differences in head circumference or femur length. The mean head circumference/abdominal circumference ratio was progressively larger for twins compared with singletons beginning at 33 weeks of gestation, which indicated a comparatively asymmetric growth pattern. At 35 weeks of gestation, the average gestational age at delivery for twins, the estimated fetal weights for the 10th, 50th, and 90th percentiles were 1960, 2376, and 2879 g for dichorionic twins, respectively, and 2180, 2567, and 3022 g for the singletons, respectively. At 32 weeks of gestation, the initial week when the mean estimated fetal weight for twins was smaller than that of singletons, 34% of twins would be classified as small for gestational age with the use of a singleton, non-Hispanic white standard. By 35 weeks of gestation, 38% of twins would be classified as small for gestational age.

CONCLUSION

The comparatively asymmetric growth pattern in twin gestations, initially evident at 32 weeks of gestation, is consistent with the concept that the intrauterine environment becomes constrained in its ability to sustain growth in twin fetuses. Near term, nearly 40% of twins would be classified as small for gestational age based on a singleton growth standard.

Dichorionic twin ultrasound surveillance: sonography every 4 weeks significantly underperforms sonography every 2 weeks: results of the Prospective Multicenter ESPRiT Study

OBJECTIVE

A 2-week ultrasound scanning schedule for monochorionic twins is endorsed widely. There is a lack of robust data to inform a schedule for the surveillance of dichorionic gestations. We aimed to determine how ultrasound scanning that is performed at 2- or 4-week intervals (or every 4 weeks before 32 weeks' gestation and every 2 weeks thereafter) may impact the prenatal detection of fetal growth restriction (FGR) and ultimately influence timing of delivery.

STUDY DESIGN

In a consecutive cohort of 789 dichorionic twin pregnancies that were recruited prospectively for the multicenter Evaluation of Sonographic Predictors of Restricted Growth in Twins study, ultrasound determination of fetal growth and interrogation of umbilical and middle cerebral artery Doppler scans were performed every 2 weeks from 24 weeks' gestation until delivery. Complete delivery and perinatal outcome data were recorded for all pregnancies. Where delivery was prompted by FGR, abnormal umbilical artery Doppler examination or poor biophysical profile and in the absence of ruptured membranes, onset of labor, preeclampsia, or antepartum hemorrhage, the delivery was considered "ultrasound-indicated." For ultrasound-indicated deliveries, detection probabilities for FGR/abnormal umbilical artery Doppler scans/poor biophysical were determined according to the interval between examinations, by the suppression if alternate examination data.

RESULTS

Among 789 dichorionic twin pregnancies, 66 pairs (8%) had an "ultrasound indicated" delivery. Detection of FGR was reduced from 88-69%, and detection of abnormal umbilical artery Doppler was reduced from 82-62% when a 4-week ultrasound schedule was simulated. Both of these reductions reached statistical significance. There was a nonsignificant trend toward a reduction in the recording of oligohydramnios with a 4-week interval between examinations.

CONCLUSION

This study suggests that the ultrasound surveillance program of every 2 weeks that is recommended currently for monochorionic twins should be extended to dichorionic gestations.

Growth discordance

Poor growth is a common problem in twin pregnancies, and management poses some unique challenges as the wellbeing of both twins have to be taken into account at all times. The decision to deliver the twins to prevent an intrauterine demise of the growth-restricted twin will, therefore, depends on the chances of intact postnatal survival of both twins. In monochorionic twins, management is complicated further by the fact that the wellbeing of one twin critically depends on that of the other twin because of the shared circulation. In the event of demise of the growth-restricted twin, the larger twin may also die or sustain brain damage because of an acute exsanguination into the feto-placental unit of its demised co-twin. In the pre-viable period, invasive fetal therapy may, therefore, be indicated to protect the appropriately growing twin.