Diagnosis of twin-to-twin transfusion syndrome, selective fetal growth restriction, twin anaemia-polycythaemia sequence, and twin reversed arterial perfusion sequence

Reduced lung function during childhood in identical twins with discordant fetal growth: a cohort study

Background

Fetal growth restriction (FGR) can negatively affect lung development, leading to increased respiratory morbidity and reduced lung function later in life. Studies regarding the impact of FGR on lung function in singletons are influenced by genetic, obstetric, and maternal factors. To overcome these confounding factors, we aim to investigate lung function in identical twins with selective FGR (sFGR).

Methods

Lung function assessments were performed in identical twins with sFGR born in our centre between March 1, 2002, and December 31, 2017, aged between 5 and 17 years. sFGR was defined as birthweight discordance ≥20%. Outcome measures consisted of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and transfer factor for carbon monoxide (DLCO) and were compared between the smaller and larger twin.

Findings

Thirty-nine twin pairs performed spirometry of sufficient quality. Median gestational age at birth was 34.3 (interquartile range (IQR) 32.1-36.0) weeks with median birthweights of 1500 (IQR 1160-1880) grams and 2178 (IQR 1675-2720) grams for the smaller and larger twin, respectively. Smaller twins had significantly lower z-scores for FEV1 (-0.94 versus -0.41, p = 0.0015), FVC (-0.56 versus -0.06, p < 0.0001) and DLCO (-0.50 versus 0.00, p < 0.0001) compared to larger co-twins.

Interpretation

Although being genetically identical, sFGR in identical twins is associated with a reduction in static and dynamic lung volume and a reduction in lung diffusion, even when taking the reduced lung volume into account. This indicates that adverse growth conditions in utero negatively affect lung development and function, potentially contributing to an increase in respiratory morbidities later in life.

Funding

The Dutch Heart Foundation and The Bontius Foundation.

Birth weight discordance in very and extremely preterm twins and the risk of neonatal hearing loss

OBJECTIVE

Birth weight (BW) discordant twins have an increased risk of mortality and morbidity. We aimed to study the effect of BW discordance on the risk of neonatal hearing loss (NHL) in very and extremely preterm twins.

STUDY DESIGN

Results of the nationwide newborn hearing screening program in Dutch Neonatal Intensive Care Units and diagnostic examination were centrally registered between 2003 and 2021 and included in this study. We selected twins and singletons with a gestational age (GA) 24- < 32 weeks. Logistic regression analyses were applied to study the effect of BW discordance on the risk of NHL adjusted for BW, GA and sex. Singletons and concordant twins, defined as a BW discordance of ≤20 %, were used as two reference groups. BW discordance was further categorized as medium (>20-30 %) and high (>30 %).

RESULTS

In total, 3430 twins (2694 concordant, 428 medium and 308 high BW discordant), and 23,114 singletons were available. Smaller newborns of high BW discordant twins showed an increased risk of NHL compared to singletons (adjusted odds ratio with 95 % confidence interval was 3.56 (2.26-5.60)). Also, smaller newborns of medium and high BW discordant twins showed an increased risk of NHL compared to concordant twins (adjusted odds ratio with 95 % confidence interval were 1.97 (1.13-3.44) and 4.17 (2.56-6.82), respectively). No other statistically significant differences were found.

CONCLUSION

BW discordance increased the risk of NHL in the smaller of the twin born very or extremely preterm. This risk increased as the weight difference increased.

Association between fetal growth-restriction and retinopathy of prematurity using a unique identical twin model

BACKGROUND

Research in singletons identified fetal growth restriction (FGR) as a risk factor for retinopathy of prematurity (ROP), but is generally subject to confounding by genetic, obstetric, and maternal factors. We investigated the effect of FGR on ROP in growth-discordant identical twins, thereby controlling for confounding factors.

METHODS

All data of monochorionic (MC) twin pairs with a birth weight discordance ≥20% born in our center between 2010 and 2021 were retrospectively reviewed for the presence of ROP. Potential risk factors for ROP were analyzed. Outcomes were compared between the smaller and larger twin.

RESULTS

We included 88 MC twin pairs with growth discordance. In 34% (30/88), both neonates were at risk of ROP. Prevalence of ROP was higher among the smaller twin compared to the larger twin, 30% (9/30) versus 13% (4/30), respectively (OR 2.8, 95% CI: 1.2-6.6). The smaller twin had a longer duration of mechanical ventilation (8 (1-20) versus 2 (1-4) days) and received their first red blood cell transfusion at an earlier postmenstrual age (29.6 (28.1-31.6) versus 30.4 (29.7-32.6) weeks).

CONCLUSIONS

In this identical twin model, FGR is associated with almost tripled odds of ROP development, suggesting that both unfavorable antenatal growth conditions and adverse neonatal outcomes affect postnatal retinal vascular proliferation.

IMPACT

Fetal growth restriction in growth-discordant identical twins is associated with almost tripled odds of developing retinopathy of prematurity in the smaller twin. Since these twins do not only differ in birth weight but also duration of mechanical ventilation and timing of the first red blood cell transfusion, both unfavorable antenatal growth conditions and adverse neonatal outcomes can affect postnatal retinal vascular proliferation. More attention for preventing retinopathy of prematurity is needed in those with fetal growth restriction who received prolonged duration of mechanical ventilation, oxygen supplementation, or a first red blood cell transfusion <32 weeks postmenstrual age.

The High-Risk Profile of Selective Growth Restriction in Monochorionic Twin Pregnancies

The present review aims to provide a critical appraisal of the sonographic diagnosis and follow-up and to evaluate the optimal clinical management of monochorionic twin pregnancies where one of the twins is complicated by selective fetal growth restriction (sFGR). The classification is based on the umbilical artery (UA) diastolic flow reflecting the outcome. If the sFGR twin has positive diastolic flow (Type I) then the prognosis is good, and it does not require close surveillance. Biweekly or weekly sonographic and Doppler surveillance and fetal monitoring are recommended strategies to detect unpredictable complications in type II and type III forms, which are defined by persistently absent/reverse end-diastolic flow (AREDF) or cyclically intermittent absent/reverse end-diastolic flow (iAREDF) in the umbilical waveforms, respectively. The latest forms are associated with an increased risk of unexpected fetal demise of the smaller twin and 10-20% risk of neurological injury in the larger twin in addition to the overall risk of prematurity. The clinical course can be affected by elective fetal therapy ('dichorinization' of the placenta with laser or selective fetal reduction) or elective delivery in the presence of severe fetal deterioration. The prediction of the clinical outcome in complicated cases of type II and III sFGR cases remains elusive. Novel routines in fetal and placental scans in order to predict neurological impairments and unexpected fetal death to optimize the delivery time-point are needed.

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.

Clinical Value and Treatment Progress of Prenatal Ultrasonography in Twin Pregnancy: A Systematic Review

Assisted reproductive technology has continued to develop in recent years, the technology has become more and more mature, and it has improved the total gestational age of the population. Assisted reproductive technology has improved twin pregnancy rates with the use of ovulation-inducing drugs. The risk factor of twins is much higher than singletons, and adverse pregnancy outcomes such as stillbirth and premature birth are more likely to occur than singletons, especially the special complications of monochorionic twins (MC), and the neonatal mortality and morbidity are also increased. Prenatal diagnosis and prognosis of twin pregnancy, as well as therapeutic interventions, are of current concern. Ultrasound can realize the understanding of intrauterine growth and development of twin pregnancy fetuses during pregnancy, can more accurately determine gestational age, organ function, and maturity, and timely detect fetal growth and development abnormalities in twin pregnancy, while the prognosis and treatment still need further improvement. The purpose of this study was to investigate the clinical value and treatment progress of prenatal ultrasound monitoring in twin pregnancy.

Changes in structural brain development after selective fetal growth restriction in monochorionic twins

OBJECTIVES

Fetal growth restriction (FGR) may alter brain development permanently, resulting in lifelong structural and functional changes. However, in studies addressing this research question, FGR singletons have been compared primarily to matched appropriately grown singletons, a design which is inherently biased by differences in genetic and maternal factors. To overcome these limitations, we conducted a within-pair comparison of neonatal structural cerebral ultrasound measurements in monochorionic twin pairs with selective FGR (sFGR).

METHODS

Structural cerebral measurements on neonatal cerebral ultrasound were compared between the smaller and larger twins of monochorionic twin pairs with sFGR, defined as a birth-weight discordance (BWD) ≥ 20%, born in our center between 2010 and 2020. Measurements from each twin pair were also compared with those of an appropriately grown singleton, matched according to sex and gestational age at birth.

RESULTS

Included were 58 twin pairs with sFGR, with a median gestational age at birth of 31.7 (interquartile range, 29.9-33.8) weeks and a median birth weight of 1155 g for the smaller twin and 1725 g for the larger twin (median BWD, 32%). Compared with both the larger twin and the singleton, the smaller twin had significantly smaller cerebral structures (corpus callosum, vermis, cerebellum), less white/deep gray matter and smaller intracranial surface area and volume. Intracranial-volume discordance and BWD correlated significantly (R²  = 0.228, P < 0.0001). The median intracranial-volume discordance was smaller than the median BWD (19% vs 32%, P < 0.0001). After correction for intracranial volume, only one of the observed differences (biparietal diameter) remained significant for the smaller twin vs both the larger twin and the singleton.

CONCLUSIONS

In monochorionic twins with sFGR, neonatal cerebral ultrasound reveals an overall, proportional restriction in brain growth, with smaller cerebral structures, less white/deep gray matter and smaller overall brain-size parameters in the smaller twin. There was a positive linear relationship between BWD and intracranial-volume discordance, with intracranial-volume discordance being smaller than BWD. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Screening, Management and Delivery in Twin Pregnancy

The following AWMF guideline (DGGG/AGG & DEGUM responsible) deals with the diagnosis, screening and management of twins as well as the timing and mode of birth.Twin pregnancies can be classified as dichorionic diamniotic (DC DA), monochorionic diamniotic (MC DA) and monochorionic monoamniotic (MC MA) which are always monochorionic.Twin pregnancies can be concordant (both twins are affected) or discordant (only one twin is affected) for chromosomal defects, malformations, growth restriction and hemodynamic disorders.Chorionicity is the prognostically most significant parameter. Monochorial twins have significantly higher risks of intrauterine morbidity and mortality compared to dichorial twins.In particular, general aspects of twin pregnancies such as dating, determination of chorionicity and amnionicity, the labeling of twin fetuses and the perinatal switch phenomenon are discussed.Routine monitoring of MC and DC twin pregnancies with ultrasound at 11-13^+ 6 weeks of gestation for chromosomal defects, invasive prenatal diagnosis, first-trimester NT or CRL discrepancies, early diagnosis of fetal anatomical defects, and management of twins with abnormalities, including selective fetocide, is described.Second trimester screening and management for preterm birth, intrauterine selective growth restriction (sFGR), classification of monochorial twins with sFGR, and management of the surviving twin after the death of the co-twin are described.Complications exclusively affecting MC twins include Twin to Twin Transfusion Syndrome (TTTS) with the important topics screening, prognosis, complications of laser therapy, timing of delivery, risks for brain abnormalities and delayed neurological development, Twin Anemia-Polycythemia Sequence (TAPS) and Twin Reversed Arterial Perfusion (TRAP) Sequence. This also includes MC MA twins as well as conjoined twins.Finally, the birth mode and time for DC and MC twin pregnancies are described.The information is summarized in 62 recommendations for action, 4 tables and 8 illustrations with comprehensive background texts.The guideline is an international guideline adaptation (ISUOG, NICE) as well as a systematic literature search and is up-to-date.

Outcomes in intervention and management of multiple pregnancies trials: A systematic review

OBJECTIVES

Twin pregnancy has risks of adverse outcomes for mother and baby. Data synthesis is required to gain evidence to aid recommendations but may be hampered by variations in outcome reporting.

STUDY DESIGN

Systematically review outcomes reported in twin pregnancy trials (PROSPERO - CRD42019133805). Searches were performed in MEDLINE, EMBASE, CINHAL, Cochrane library (inception-January 2019) for randomised control trials or their follow-up studies reporting prediction, prognosis, intervention or management outcomes in twin pregnancy. The study characteristics, outcomes definitions and measurements were extracted and descriptively analysed.

RESULTS

49 RCTs and 8 follow-up studies evaluated 21 interventions, 1257 outcomes, categorised into 170 unique outcomes. 65 % of trials included all twin pregnancies, 12 % DCDA and 11 % MCDA only or MCMA and MCDA. Five (9 %) papers were prediction/ prognosis RCT's and 52 (91 %) related to an intervention. Of interventions, 40 (77 %) were medical, 34 (85 %) for preterm birth; 12 (23 %) surgical, 6 (50 %) related to TTTS interventions (83 % for monochrorionic studies). Commonest domains were: 'Neonatal' 77 %, 'Delivery' 70 % and 'Survival' 67 %. Least reported were longer term outcomes for 'Infant' or 'Parental'.

CONCLUSIONS

Twin pregnancy outcomes are diverse and complex. This is related to the need to address maternal, single and double fetal outcomes and different types of chorionicity. The lack of outcome standardisation in selection, definition and reporting hinders evidence synthesis and the selection of outcomes important to women and health care professionals thus limiting the effectiveness of research.

Management of Twin Pregnancies: A Comparative Review of National and International Guidelines

Importance

Twin pregnancies are associated with a higher risk of perinatal mortality and morbidity compared with singleton and require more intensive prenatal care.

Objective

The aim of this study was to review and compare the recommendations from published guidelines on twin pregnancies.

Evidence Acquisition

A descriptive review of guidelines from the Royal College of Obstetricians and Gynaecologists, the International Society of Ultrasound in Obstetrics and Gynecology, the Royal Australian and New Zealand College of Obstetricians and Gynaecologists, the National Institute for Health and Care Excellence, the Institute of Obstetricians and Gynaecologists of the Royal College of Physicians of Ireland, the International Federation of Gynecology and Obstetrics, the Society of Obstetricians and Gynaecologists of Canada, and the American College of Obstetricians and Gynecologists on the management of twin pregnancies was conducted.

Results

All the guidelines highlight the importance of an accurate assessment of chorionicity, amnionicity, and gestational age in the first trimester. They also recommend the performance of nuchal translucency and a detailed anomaly scan. The ultrasound surveillance protocol is similar in all guidelines, that is, every 2 weeks for monochorionic and every 4 weeks for dichorionic twins. On the other hand, there are differences regarding the timing and mode of delivery, especially in monochorionic diamniotic twins, in the definition and management of fetal growth discordance, the use of cervical length to screen for preterm birth, and the timing of corticosteroids' administration.

Conclusions

The differences in the reviewed guidelines on the management of twin pregnancies highlight the need for an adoption of an international consensus, in order to improve perinatal outcomes of twin pregnancies.

The Use of Sequential Integrated Screening to Stratify Risk in Monochorionic-Diamniotic Twin Pregnancies

OBJECTIVE

This study aimed to identify differences in sequential integrated screening and early ultrasound markers in monochorionic/diamniotic (MC/DA) pregnancies complicated by twin-to-twin transfusion syndrome (TTTS) and unequal placental sharing (UPS).

STUDY DESIGN

Retrospective cohort study of MC/DA pregnancies evaluated between January 2012 and July 2017 at the University of California San Francisco. MC/DA pregnancies with ultrasound surveillance up to 26 weeks who participated in the California Prenatal Screening Program (CPSP) were included. Pregnancies with structural or genetic anomalies were excluded. UPS was defined as an intertwin growth discordance ≥20%. Intertwin nuchal translucency (NT) discordance was calculated by the absolute value of the difference of the NT of cotwins. Kruskal-Wallis or ANOVA testing was performed where appropriate, and negative binomial regression models were chosen to test for differences in mean biomarker levels by outcome group.

RESULTS

A total of 191 MC/DA pregnancies were included; 85 were affected by TTTS, 35 by UPS, and 71 controls. Significant differences in intertwin NT discordance in pregnancies complicated by TTTS and UPS compared with controls (p = 0.007) were found. TTTS cases had a mean NT discordance greater than two times that of controls (p = 0.04), while UPS cases had a value more than three times greater (p = 0.003). There was a statistically significant difference in mean second trimester human chorionic gonadotropin (hCG) between the cohorts (p = 0.0002) with TTTS cases having a mean second trimester hCG value 1.5 greater than both controls (p < 0.001) and UPS cases (p = 0.001). Analysis showed a significant difference in mean second trimester inhibin between the three cohorts (p = 0.029). Pregnancies complicated by UPS had a mean second trimester inhibin 1.5 times greater than controls (p = 0.010).

CONCLUSION

Our study shows that there are unique differences in early ultrasound and sequential integrated serum markers between MC/DA gestations complicated by TTTS and UPS versus those unaffected.

KEY POINTS

· Differences exist in sequential integrated screening markers in monochorionic-diamniotic twin pregnancies.. · Early risk stratification of monochorionic-diamniotic twin pregnancies may be possible.. · Sequential integrated screening testing can provide useful information to clinicians when evaluating monochorionic-diamnitoic twin pregnancies..

Placental glucose transporter 1 and 3 gene expression in Monochorionic twin pregnancies with selective fetal growth restriction

Background

In monochorionic twin (MC) gestations with selective fetal growth restriction (FGR), the discordant fetal growth usually is due to unequal placental sharing. Glucose, which is essential for oxidative metabolism in the growing placenta and fetus, is transferred from maternal blood by facilitated carrier-mediated diffusion via glucose transporters (GLUTs). How the GLUTs expression varies in the two placenta territories manifests discordant perfusion in MC twin pregnancy with selective FGR is unknown. This study evaluates the human placental GLUT1 and GLUT3 gene expression in MC twin gestations with selective FGR.

Methods

MC twin pregnancy with selective FGR was defined as the presence of inter-twin birth weight discordance of > 25% and the smaller twin with a birth weight less than the 10th percentile in third trimester. Fetal umbilical artery Doppler was checked within 1 week before delivery in the two fetuses. An abnormal umbilical artery Doppler was defined as persistently absent or reverse end-diastolic flow (UA-AREDF). GLUT1, GLUT3 and HIF-1α gene expression were assayed in each twin’s placental territories. The inter-twin placental gene expression ratio was calculated as the placenta GLUTs or HIF-1α expression level of the selective FGR twin divided by expression level of the appropriate-for-gestational-age (AGA) cotwin. Higher gene expression ratio means elevated gene expression in the selective FGR twin’s placenta territory compared to AGA twin’s placenta territory.

Results

15 MC twin gestations with selective FGR including nine with normal (group 1) and six with abnormal selective FGR twin UA Doppler (group 2) were included into this study. The GLUT3 and HIF-1α gene expression are significantly elevated in selective FGR twin’s placenta territory in group 2 twin pregnancies (mean gene expression ratio as 2.23 and 1.65, p values as 0.015 and 0.045, respectively), but not in in group 1 twin pregnancies.

Conclusion

The upregulation of placental GLUT3 gene expression in selective FGR fetus with abnormal UA Doppler may be due to hypo-perfusion which is mediated by up -regulation of HIF-1α gene expression.

Respiratory distress syndrome and bronchopulmonary dysplasia after fetal growth restriction: Lessons from a natural experiment in identical twins

BACKGROUND

Fetal growth restriction (FGR) is thought to negatively affect lung development resulting in increased respiratory morbidity. However, research performed in singletons is often limited by a certain level of bias caused by individual differences in genetic constitution, obstetrical and maternal factors.

METHODS

Respiratory morbidity was compared between the smaller and the larger twin in monochorionic twins with selective fetal growth restriction (sFGR), defined as a birth weight discordance ≥ 20%, born in our center between 2010 and 2019 in this retrospective study. Respiratory distress syndrome (RDS) was diagnosed based on the clinical picture of a neonate with respiratory failure requiring mechanical ventilation and/or surfactant, confirmed by a chest X-ray. Bronchopulmonary dysplasia (BPD) was diagnosed when the neonate required treatment with >21% oxygen for at least 28 days.

FINDINGS

Median gestational age at birth for the 94 included pregnancies was 32.4 (IQR 30.4-34.3) weeks. Within-pair analyses showed that the prevalence of RDS was lower in the smaller twin compared to the larger twin, 19.1% (18/94) vs 34.0% (32/94), respectively (p = 0.004). The odds of RDS for the larger twin was doubled (OR 2.1 (CI95% 1.3-3.5). In contrast, the rate of BPD in the smaller twin was higher as opposed to the larger twin, 16.7% (15/90) vs 6.7% (6/89), respectively (p = 0.008), with a more than doubled odds (OR 2.5 (CI95% 1.3-4.9)).

INTERPRETATION

Despite being genetically identical, sFGR twins have different respiratory outcomes. Adverse growth condition in utero in the smaller twin is associated with a reduced odds of RDS at birth but a more than doubled odds of BPD, reflecting the pathophysiologic adverse effect of growth restriction on lung development.

FUNDING

The Dutch Heart Foundation (2017T075).

Vascular anastomoses in intrauterine growth in monochorionic twins

Objectives To evaluate the impact of placental anastomoses on the intrauterine growth of monochorionic (MC) twins. Methods A prospective study was conducted in a group of 53 MC twins. Intrapartally umbilical cords were clamped to identify placental sides corresponding to each twin. The postnatal dye injection technique was administered to evaluate vascular anastomoses, their number and type and visualize placental territory sharing patterns. Data from digital analysis were correlated with obstetrical follow-up. Results Vascular anastomoses were revealed in 88.7% of cases. Arteriovenous (AV) anastomoses occurred in 75.4% and arterioarterial (AA) in 71.1% while venovenous (VV) in 26.4%. In the subgroup of MC twins without placental anastomoses, significantly higher birthweight difference and discordance were revealed when compared to MC twins without anastomoses (382.0 vs. 22 g; P = 0.03 and 49.14% vs. 16.02%; P = 0.03). On the other hand, in subgroups of MC twins with at least one AA anastomosis, twins' birthweights were similar (p = ns) despite significantly higher placental territory sharing discordance (30.44% vs. 15.81%; P = 0.31). Conclusions Vascular anastomoses have a major impact on the intrauterine growth of MC twins. In certain cases, they may cause specific complications; however, in general, they regulate intertwin blood exchange and may compensate unequal placental territory.

Middle Cerebral Artery Doppler Velocimetry for the Diagnosis of Twin Anemia Polycythemia Sequence: A Systematic Review

Twin anemia polycythemia sequence (TAPS) is a rare complication of monochorionic diamniotic (MCDA) twins. Middle cerebral artery peak systolic velocity (MCA-PSV) measurements are used to screen for TAPS while fetal or neonatal hemoglobin levels are required for definitive diagnosis. We sought to perform a systematic review of the efficacy of MCA-PSV in diagnosing TAPS. Search criteria were developed using relevant terms to query the Pubmed, Embase, and SCOPUS electronic databases. Publications reporting diagnostic characteristics of MCA-PSV measurements (i.e., sensitivity, specificity or receiver operator curves) were included. Each article was assessed for bias using the Quality Assessment of Diagnostic Accuracy Studies II (QUADAS II) tool. Results were assessed for uniformity to determine whether meta-analysis was feasible. Data were presented in tabular form. Among publications, five met the inclusion criteria. QUADAS II analysis revealed that four of the publications were highly likely to have bias in multiple areas. Meta-analysis was precluded by non-uniformity between definitions of TAPS by MCA-PSV and neonatal or fetal hemoglobin levels. High-quality prospective studies with consistent definitions and ultrasound surveillance protocols are still required to determine the efficacy of MCA-PSV in diagnosing TAPS. Other ultrasound findings (e.g., placenta echogenicity discordance) may augment Doppler studies.

Twin-twin transfusion syndrome in the era of fetoscopic laser surgery: antenatal management, neonatal outcome and beyond

Introduction: Twin-twin transfusion syndrome (TTTS) is a devastating complication of monochorionic twin pregnancy and remains a major challenge for worldwide fetal medicine specialists. In TTTS, intertwin transfusion through vascular anastomoses in the shared placenta leads to severe hemodynamic imbalance. This review summarizes the current knowledge of TTTS.Areas covered: The most recent insights concerning the management of TTTS, as well as fetal and neonatal complications are described. Relevant articles were selected based on a Pubmed search using the keywords below. Understanding of the underlying pathophysiology has improved greatly as a result of placental injection studies. Advancements in antenatal management have led to increased perinatal survival and a decreased incidence of neonatal complications, including brain injury and neurodevelopmental impairment.Expert opinion: Further opportunities for improvement comprise technological innovations in laser procedures and the prevention of preterm rupture of membranes with subsequent prematurity. A noninvasive treatment such as high-intensity focused ultrasound (HIFU) seems to hold promise for the future treatment of TTTS. Fetal MRI studies are important to improve our understanding of fetal brain injury and should relate their findings to long-term neurodevelopment. International collaboration and centralization of care are of paramount importance to ensure the best care for our patients.

Twin anemia-polycythemia sequence and routine monitoring practices amongst maternal-fetal medicine specialists in the United States: an initial investigation

Background The purpose of this initial investigation was to begin to understand the routine twin anemia-polycythemia sequence (TAPS) monitoring practices of maternal-fetal medicine specialists (MFM specialists) in the United States in the absence of a formal guideline. Methods This study used an anonymous, online survey of 90 MFM specialists who were practicing in the United States. A $5 gift card to an online store was used to incentivize participants. Descriptive statistics were calculated. Results All MFM specialists reported at least some familiarity (100.00%) with TAPS. Most participants (92.94%) were familiar with methods for monitoring patients for TAPS and nearly all (97.50%) responded that they use 'Doppler MCA-PSV' to make a prenatal TAPS diagnosis. Nearly two-thirds of MFM specialists surveyed (65.06%) reported performing regular TAPS monitoring for patients with monochorionic-diamniotic (MCDA) pregnancies. Conclusion Despite no formal guidelines, the majority of American MFM specialists surveyed are using routine TAPS screening in their management of MCDA twin pregnancies, suggesting that the MFM specialists included in this study consider it a valuable diagnostic tool. Future research should further explore this possible trend toward routine TAPS monitoring amongst MFM specialists in the United States, as well as the potential value of routine TAPS monitoring in MCDA pregnancy.

Prediction of adverse pregnancy outcome in monochorionic diamniotic twin pregnancy complicated by selective fetal growth restriction

OBJECTIVE

To identify key factors associated with adverse perinatal outcome in monochorionic diamniotic twin pregnancy complicated by selective fetal growth restriction (sFGR).

METHODS

This was a retrospective cohort study of all monochorionic diamniotic twin pregnancies diagnosed with sFGR at ≥ 16 weeks' gestation, in a single tertiary referral center between March 2000 and May 2015. The presence of coexisting twin-twin transfusion syndrome (TTTS) was noted. Fetal biometry and Doppler indices, including those of the umbilical artery (UA) and ductus venosus (DV), were recorded at the time of diagnosis. The type of sFGR was diagnosed according to the pattern of end-diastolic flow in the UA of the smaller twin. DV pulsatility indices for veins (DV-PIV) were converted to Z-scores and estimated fetal weight values to centiles, to correct for gestational age (GA). Cox proportional hazards model was used to examine for independent predictors of adverse perinatal outcome, which was defined according to survival and included both intrauterine fetal demise and neonatal death of the FGR twin.

RESULTS

We analyzed 104 pregnancies, of which 66 (63.5%) were diagnosed with Type-I and 38 (36.5%) with Type-II sFGR at initial presentation. In pregnancies complicated by Type-II sFGR, the diagnosis of sFGR was made earlier than in those complicated by Type-I sFGR (mediam GA, 19.6 vs 21.5 weeks; P = 0.012), and Type-II sFGR was associated with increased risk of adverse perinatal outcome (intrauterine demise of the smaller twin, 34.2% vs 10.6%; P = 0.004). Twin pregnancies complicated by sFGR resulting in perinatal demise had a significantly earlier diagnosis (P = 0.002) and lower birth-weight centile of the smaller twin (P < 0.01), those with Type-I sFGR had earlier GA at delivery (P = 0.007) and those with Type-II sFGR had higher DV-PIV Z-score of the smaller twin (P = 0.003), when compared with pregnancies resulting in live birth. Coexisting TTTS had no significant impact on the perinatal outcome of pregnancies diagnosed with either Type-I or Type-II sFGR (P > 0.05 for both). Earlier GA at diagnosis (hazard ratio (HR), 0.70 (95% CI, 0.56-0.88); P = 0.002), Type-II sFGR (HR, 3.53 (95% CI, 1.37-9.07); P = 0.008) and higher DV-PIV Z-score (HR, 1.36 (95% CI, 1.12-1.65); P = 0.001) were significantly associated with increased risk of adverse perinatal outcome of the smaller twin.

CONCLUSIONS

Pregnancies complicated by Type-II sFGR are diagnosed significantly earlier and are associated with increased risk of adverse perinatal outcome compared with those with Type-I sFGR. Coexisting TTTS has no significant impact on the perinatal outcome of pregnancies diagnosed with either Type-I or Type-II sFGR. Earlier GA at diagnosis, Type-II sFGR and higher DV-PIV Z-score are associated significantly with increased risk of adverse perinatal outcome of the smaller twin. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Placental erythropoietin expression is upregulated in growth-restricted fetuses with abnormal umbilical artery Doppler findings: a case-control study of monochorionic twins

BACKGROUND

We previously reported that fetal plasma erythropoietin (EPO) concentrations are significantly increased in growth-restricted fetuses with abnormal umbilical artery (UA) Doppler. During hypoxia in an ovine model, the primary site of fetal EPO synthesis was switched from the kidneys to the placenta. Therefore, we designed this study to evaluate human placental EPO gene expression and the correlation to fetal serum EPO concentration in growth-restricted fetuses in a monochorionic (MC) twin model.

METHODS

In MC twin pairs, selective intrauterine growth restriction (sIUGR) was defined as the presence of (i) birth weight discordance of > 20% and (ii) a smaller twin with a birth weight less than the 10th percentile. Fetal UA and middle cerebral artery (MCA) Doppler were checked within 1 week before delivery. An abnormal UA Doppler was defined as persistently absent or reverse end-diastolic flow. Cerebroplacental ratio (CPR) was defined as MCA-pulsatility index (PI)/UA-PI. Fetal plasma EPO concentrations were measured in cord blood, and EPO gene expression was assayed in each twin's placental territory. The intertwin plasma EPO ratio was calculated as the cord plasma EPO level of the smaller (or sIUGR) twin divided by the EPO concentration of the larger (or appropriate-for-gestational-age (AGA)) twin, and the intertwin placental EPO gene expression ratio was calculated similarly.

RESULTS

Twenty-six MC twins were analyzed, including normal twins (Group 1, n = 9), twins with sIUGR without UA Doppler abnormalities (Group 2, n = 9), and twins with sIUGR and UA Doppler abnormalities (Group 3, n = 8). The CPRs of smaller (sIUGR) fetuses were significantly decreased in Group 3 MC twins (p < 0.001), but not significantly different between Group 1 and Group 2. The highest fetal plasma EPO ratio and placental EPO gene expression ratio were identified in Group 3 MC twins (p < 0.001). The placental EPO gene expression ratios were significantly correlated with the fetal plasma EPO ratios (Pearson's correlation test, p = 0.004).

CONCLUSION

This study provides evidence of increased placental EPO expression in MC twin fetuses with sIUGR and abnormal UA Doppler. Future studies are needed to confirm the similar role of placental EPO in severe IUGR singletons.

Risk factors for fetal death after radiofrequency ablation for complicated monochorionic twin pregnancies

OBJECTIVE

Radiofrequency ablation (RFA) is a management alternative for complicated monochorionic twin pregnancies. The purpose of this study is to evaluate risk factors for fetal death after RFA.

METHODS

An observational study was performed to document the perinatal outcomes of all cases undergoing fetal reduction using RFA from 2010 to 2016 at the Shanghai First Maternity and Infant Hospital. A multiple regression model was built to identify predictors of the death of the remaining fetus after RFA.

RESULTS

A total of 183 patients treated with RFA for fetal reduction were analyzed, including 53 selective intrauterine growth restriction, 35 twin-twin transfusion syndrome, 36 dichorionic triamniotic triplets, 24 monochorionic twins discordant for fetal anomaly, and 35 twin reversed arterial perfusion. The prevalence of fetal death after RFA was 23% (43:183). The occurrence of fetal death after RFA was independently associated with more than 2 cycles of RFA coagulation (OR 3.46; 95% CI, 1.34-8.94; P = .01).

CONCLUSION

More than 2 cycles of RFA coagulation is the only independent risk factors of fetal death after RFA.

ACR Appropriateness Criteria® Multiple Gestations

Women with twin or higher-order pregnancies will typically have more ultrasound examinations than women with a singleton pregnancy. Most women will have at minimum a first trimester scan, a nuchal translucency evaluation scan, fetal anatomy scan at 18 to 22 weeks, and one or more scans in the third trimester to evaluate growth. Multiple gestations are at higher risk for preterm delivery, congenital anomalies, fetal growth restriction, placenta previa, vasa previa, and velamentous cord insertion. Chorionicity and amnionicity should be determined as early as possible when a twin pregnancy is identified to permit triage of the monochorionic group into a closer surveillance model. Screening for congenital heart disease is warranted in monochorionic twins because they have an increased rate of congenital cardiac anomalies. In addition, monochorionic twins have a higher risk of developing cardiac abnormalities in later gestation related to right ventricular outflow obstruction, in particular the subgroups with twin-twin transfusion syndrome or selective intrauterine growth restriction. Monochorionic twins have unique complications including twin-to-twin transfusion syndrome, twin embolization syndrome, and acardius, or twin-reversed arterial perfusion sequence. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Selective intrauterine growth restriction in monochorionic twins: changing patterns in umbilical artery Doppler flow and outcomes

OBJECTIVES

To describe changes in umbilical artery (UA) Doppler flow in monochorionic diamniotic (MCDA) twins affected by selective intrauterine growth restriction (sIUGR), to correlate Doppler findings with pregnancy course and perinatal outcome, and to report postnatal follow-up.

METHODS

This was a retrospective study of 140 MCDA twins with sIUGR. UA end-diastolic flow, defined as Doppler waveform pattern Type I (persistently positive), Type II (persistently absent or persistently reversed) or Type III (intermittently absent or intermittently reversed), was recorded at first examination and monitored weekly until double or single intrauterine fetal death (IUFD), bipolar cord coagulation or delivery. All neonates had an early neonatal brain scan, magnetic resonance imaging, when indicated, and neurological assessment during infancy. Rates (per 100 person-weeks) and hazard ratios (HR) of IUFD in the IUGR twin in each pregnancy were calculated considering UA Doppler pattern as a time-dependent variable.

RESULTS

At first examination, there were 65 cases with UA Doppler waveform pattern Type I, 62 with Type II and 13 with Type III. Of the 65 Type-I cases, 48 (74%) remained stable, while 17 (26%) changed to either Type II absent (14%), Type II reversed (9%) or Type III (3%). Of 62 Type-II cases (47 with absent and 15 with reversed flow), 33 (53%) remained stable (18 with absent and all 15 with reversed flow). The 29 Type-II absent cases which changed became Type II reversed (24/47, 51%) or Type III (5/47, 11%). All 13 Type-III cases remained stable. Compared with Type I, the risk of IUFD (adjusted for estimated fetal weight discordance and amniotic fluid deepest vertical pocket) was highest when the pregnancy was or became Type II reversed (HR, 9.5; 95% CI, 2.7-32.7) or Type II absent (HR, 4.3; 95% CI, 1.3-14.3). Mild neurological impairment was more prevalent in the IUGR twin than in the large cotwin (7% vs 1%, P = 0.02).

CONCLUSIONS

Risk stratification based on UA Doppler is useful for planning ultrasound surveillance. However, patterns can change over time, with important consequences for management and outcome. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Pathological Findings in Feto-maternal Hemorrhage

Feto-maternal hemorrhage (FMH) is the cause of late fetal death in 1.6%-11% of cases. In spite of this high frequency, its pathological features have received little attention. The definitive diagnosis of lethal FMH requires confirmation of sufficient fetal blood volume loss. This is determined by tests such as the Kleihauer-Betke test, which may not have been obtained or not have been available before the autopsy. The pathologist may offer a tentative diagnosis of FMH from the autopsy findings. The objective of this study was to better characterize the placental and fetal autopsy findings in lethal FMH. This was a retrospective study of 17 cases of FMH proven by a positive Kleihauer-Betke test. The cases were selected from the autopsy files of the Department of Pathology, Centre Hospitalier Universitaire de Bordeaux. The pathological reports as well as the placental and fetal photographs and the microscopic slides of each case were systematically reviewed. The fetal autopsy findings in FMH are characterized by a eutrophic pale macerated fetus, low liver weight, absent intrathoracic petechiae, increased extramedullary hematopoiesis in the liver and kidney, and increased circulating nucleated red blood cells. The placenta shows an increased frequency of intervillous thrombi. Although nonpathognomonic, some of the pathological features are strongly suggestive of FMH. When the latter is present, a Kleihauer-Betke test should be performed, even some days after the delivery.