Twin chorionicity and the risk of adverse perinatal outcome

Term twin birth - impact of mode of delivery on outcome

INTRODUCTION

The main aims of this study were to compare maternal and neonatal outcomes in term twin birth according to the planned mode of delivery and to study the effects of chorionicity and inter-twin delivery time on neonatal outcome.

MATERIAL AND METHODS

A single-center cohort study of 495 women with twin deliveries at ≥37⁺⁰ weeks of gestation. Term twin deliveries were divided into a trial of labor group (TOL, 69.3%) and a planned cesarean section (CS) group (30.7%). The primary outcomes were maternal and neonatal morbidity.

RESULTS

80.8% of women attempting TOL achieved vaginal birth. In the TOL group, mothers had less bleeding [median 500 mL (range 150-2700 mL) vs. 950 mL (range 150-3500 mL), p < 0.001) and fewer surgical complications (3.2% vs. 8.6%, p = 0.011), whereas second twins more often had five-minute Apgar scores of <7 (5.0% vs. 0%, p = 0.002) or umbilical artery pH < 7.05 (5.7% vs. 0%, p = 0.003), compared with the planned CS group. There was a slight, non-significant tendency for more NICU admissions in the TOL group, yet the need for NICU treatment was infrequent in the whole study material. Outcomes among dichorionic (DC) second twins were similar to those in the whole material, but among monochorionic (MC) second twins there were no differences between the TOL and planned CS groups. In secondary analysis, a five-minute Apgar score <7 occurred significantly more often in the DC group among second twins if the inter-twin delivery time exceeded 30 min.

CONCLUSIONS

TOL is a good option for women with twin pregnancy at term, regardless of chorionicity. Active management of labor for the second twin is important, also in DC births. Maternal outcomes were more favorable with TOL and although low Apgar scores and low umbilical blood pH may be more frequent after TOL - especially with the second twin - serious neonatal morbidity is rare and does not differ from that after planned CS.

Placental Up-Regulation of Leptin and ARMS2 is Associated with Growth Discordance in Monochorionic Diamniotic Twin Pregnancies

Fetal growth discordance is a relatively common complication of monochorionic diamniotic (MCDA) twin pregnancies and is caused by a combination of maternal and placental factors. The aim of the study was to survey placental gene expression patterns and identify genes associated with growth discordance. Clinical samples comprised eight growth-discordant MCDA twin placentas (31+3–34+4 weeks gestational age) and six growth-concordant twin placentas (31+2–37 weeks gestational age). Gene expression libraries were constructed from placental biopsy samples and analyzed by RNA-sequencing. The distribution and relative abundance of mRNA transcripts expressed in the smaller and larger placentas from growth-discordant and concordant MCDA twins was remarkably similar. However, leptin (LEP) and age-related maculopathy susceptibility 2 (ARMS2) mRNA levels were exclusively up-regulated in all of the eight smaller growth-discordant twin placentas. Quantitative real-time PCR of independent biopsy samples confirmed the levels of differential mRNA expression for both genes. Immunohistochemical analysis of tissue sections from matching twin placentas showed increased leptin expression in 5–10% of blood vessel cells of the smaller placenta and marginally higher levels of ARMS2 expression in the microvillous membrane of the smaller placenta. Based on these findings, we speculate that up-regulation of leptin and ARMS2 forms part of an important survival mechanism to compensate for placental growth discordance. Since, leptin and ARMS2 are both expressed as soluble proteins, they may have clinical potential as measurable biomarkers for predicting the onset of growth discordance in MCDA twin pregnancies.

Developmental and behavioral outcomes of uncomplicated monochorionic diamniotic twins born in the third trimester

BACKGROUND

Relatively little is known about the neurodevelopmental and behavioral outcomes of monochorionic diamniotic (MCDA) twin pregnancies where there are no antenatal complications peculiar to monochorionicity or prematurity.

METHODS

Twenty-two MCDA twins (44 children) with an average age of 4.3 years, and with no antenatal complications detected by 28 weeks of gestation, were recruited from a feto-maternal unit database. Parents completed a battery of neurodevelopmental and behavioral assessment questionnaires.

RESULTS

Eighteen children (41%) were identified as having developmental or behavioral concerns, predominantly of mild severity, which in turn were associated with a lower birth weight of medium effect size (Cohen's d=0.59).

CONCLUSION

MCDA twins delivered in the third trimester with no antenatal monochorionic complications in the first two trimesters appear to be at risk for subtle neurodevelopmental difficulties, associated with a lower birth weight. Ongoing developmental surveillance of these children during preschool-age is indicated for early identification and intervention.

The Outcome of Monochorionic Diamniotic Twins Discordant at 11 to 13+6 Weeks' Gestation

BACKGROUND

Monochorionic diamniotic (MCDA) twin pregnancies are associated with adverse perinatal outcome. Intertwin discordances at the time of nuchal translucency (NT) screening may have a value in the prediction of fetal loss or twin-to-twin transfusion syndrome. We aimed to determine the ability of intertwin NT and crown rump length (CRL) discordances among MCDA twins to predict adverse outcomes.

MATERIAL AND METHODS

All MCDA twins with a documented routine ultrasound at 11 to 13+6 weeks' gestation, and known pregnancy outcome between August 2003 and August 2012 were included. Receiver operating characteristic curves were used to determine the ideal NT and CRL discordances cut-off points that maximized the ability to predict adverse outcome, which was defined as any of: death of one or both twins, twin-to-twin transfusion syndrome, or estimated fetal weight or birth weight discordances ≥25%.

RESULTS

Of the 89 cases, 20 (22.5%) had at least one adverse outcome. NT discordance was more discriminatory of adverse outcome than was CRL discordance. The optimal values for predicting any adverse outcomes for NT were >23.7% and for CRL >3.5%. The positive predictive values for NT (52.4%) and CRL (29.8%) screening were relatively low; however, the lack of either NT or CRL discordances was more reassuring, with negative predictive values of 86.8% and 86.4%, respectively.

CONCLUSIONS

NT discordance is more predictive for adverse fetal outcome in MCDA twins than CRL discordance. Neither NT nor CRL discordance are likely to modify the intensive monitoring required for these very high-risk pregnancies.

Uncommon complications of monochorionic twin pregnancies: Twin reversed arterial perfusion sequence

Introduction

Twin reversed arterial perfusion (TRAP) sequence occurs when there is one non-viable twin without cardiac structures and a viable pump twin that perfuses the acardiac mass. This study aims to investigate the management and immediate neonatal outcomes for monochorionic multiple pregnancies complicated by TRAP referred to the NSW Fetal Therapy Centre (NSW FTC).

Methods

Retrospective cohort study of multiple pregnancies referred to NSW FTC between April 2006 and April 2014, reviewing data for cases of TRAP sequence (n = 19, including two triplet cases) compared to a timeframe matched sample of uncomplicated monochorionic diamniotic (MCDA) twin pregnancies managed in the unit (n = 45).

Results

Primary management of the 19 TRAP cases was expectant management in 10 (53%), radiofrequency ablation (RFA) in 6 (32%), and bipolar cord coagulation, amniodrainage and termination of pregnancy in 1 case each. 1 of 6 RFA cases had pump twin demise <1 week post-procedure. Average gestation at birth (35.1 ± 5.0 vs. 35.0 ± 2.8 weeks) and mean birthweight (2157 ± 1019 g vs. 2245 ± 537 g) were similar between TRAP pump fetuses and uncomplicated MCDA cases. Pump twin survival was 81% (twins only) compared to 98% for uncomplicated MCDA twins (P = 0.02), and in 5 of 19 (26%) TRAP pregnancies the pump fetus had a congenital anomaly.

Conclusion

Mean gestational age at birth and mean birthweight were similar for both TRAP and uncomplicated MCDA pregnancies. TRAP cases, however, had higher perinatal mortality, and high rates of congenital anomaly. The overall neonatal outcome at NSW FTC for TRAP cases is similar to reported international outcomes.

Impact of recipient twin preoperative myocardial performance index in twin-twin transfusion syndrome treated with laser. J Matern Fetal Neonatal Med 2016;30:767-771. [PMID: 27150066 DOI: 10.1080/14767058.2016.1187124]

OBJECTIVE

To validate the efficacy of laser therapy for twin-twin transfusion syndrome (TTTS) in the treatment of recipient twin cardiomyopathy and investigate whether severity of preoperative cardiomyopathy can predict fetal survival postoperatively.

STUDY DESIGN

Retrospective study of monochorionic-diamniotic (MCDA) pregnancies complicated by TTTS treated by selective fetoscopic laser photocoagulation (SFLP) performed between March 2010 and October 2014 at a single center. The recipient right ventricular (RV) and left ventricular (LV) myocardial performance index (MPI) were measured both pre- and postoperatively. The data were analyzed with the Wilcoxon signed rank and parametric t-tests.

RESULTS

Forty-three women met inclusion criteria during the study period. There was a substantial improvement in recipient LV (0.57 ± 0.13 versus 0.43 ± 0.13, p ≤ 0.0001) and RV (0.60 ± 0.16 versus 0.49 ± 0.18, p ≤ 0.0001) MPI postoperatively (median = 8 days). Recipient preoperative LV and RV MPI did not correlate with recipient or donor survival at 24 hours, 7 days or at birth. Thirty-seven recipients (95%) showed improvement in either LV or RV MPI and 22 (56%) showed complete resolution of cardiac dysfunction.

CONCLUSION

Laser treatment for TTTS causes rapid improvement in the cardiac function of recipient fetuses. The severity of recipient preoperative MPI does not correlate with survival of either twin postoperatively.

The History of Treatment of Twin-to-Twin Transfusion Syndrome

Historical suggestions of twin-to-twin transfusion syndrome (TTTS) date back to the early 17th century. Placental anastomoses were first reported in 1687; however, it was Schatz who first identified their importance in 1875. He recognized ‘the area of transfusion’ within the ‘villous district’ of the placenta, which he named the ‘third circulation’. This article describes how the management of TTTS has evolved as we have gained a more sophisticated understanding and appreciation of the complex vascular anastomoses that exist in monochorionic twin placentae. Currently, fetosopic laser occlusion is the preferred treatment option for TTTS.

Very Low Birth Weight Monochorionic Diamniotic Twins as a Risk Factor for Symptomatic Patent Ductus Arteriosus

BACKGROUND

Some prior studies have shown that symptomatic patent ductus arteriosus (sPDA) is highly familial. Although it is estimated that both genetic and environmental factors may contribute to sPDA, evidence is still lacking.

OBJECTIVE

The aim of this study was to determine the risk factors for sPDA, focusing on the genetic and in utero environment by analyzing very low birth weight (VLBW) singletons and twins.

METHODS

This retrospective case-control study reviewed the medical records of 445 VLBW infants (25 weeks ≤ gestational age <32 weeks, 600 g ≤ birth weight <1,500 g) and compared the incidence of sPDA among monochorionic diamniotic (MD) twins (n = 65), dichorionic diamniotic (DD) twins (n = 66), and singletons (n = 314).

RESULTS

Stepwise multiple regression analysis showed that twin siblings (p = 0.001), gestational week (p < 0.001), antenatal steroid use (p = 0.021), and premature rupture of membranes (p = 0.002) were independent predictors of sPDA. Incidence of sPDA in MD twin siblings was significantly higher than that in singletons (p < 0.01), whereas no significant difference was found between singletons and DD twins or between MD and DD twins.

CONCLUSIONS

The current results show that being a VLBW MD twin is an independent risk factor for sPDA, and that both genetic and in utero environmental factors may contribute to its development.

The North American Fetal Therapy Network Consensus Statement: Management of Complicated Monochorionic Gestations

The North American Fetal Therapy Network is a consortium of 30 medical institutions in the United States and Canada with established expertise in fetal therapy and other forms of multidisciplinary care for complex fetal disorders. This publication is the third in a series of articles written by NAFTNet about monochorionic pregnancies. In this article, we provide the general obstetric practitioner with information regarding management options available for complications of monochorionic gestations. This information may be useful for a better understanding of the pathophysiology of the various conditions, for better patient counseling, for timely referral to a regional treatment center, and for ongoing comanagement after treatment.

Discordant Growth of Monozygotic Twins Starts at the Blastocyst Stage: A Case Study

Discordant growth is a common complication of monochorionic/diamniotic pregnancies; in approximately 50% of cases, the cause is unknown. The case presented here suggests that discordant growth of monozygotic twins could start during preimplantation development. Two inner cell masses (ICMs) within the same blastocyst may originate in uneven splitting of a single “parental” ICM, or the two ICMs may be formed independently de novo. We studied the transcriptomes of two morphologically distinct ICMs within a single blastocyst using high-resolution RNA sequencing. The data indicated that the two ICM were at different stages of development; one was in the earliest stages of lineage commitment, while the other had already differentiated into epiblast and primitive endoderm. IGF1-mediated signaling is likely to play a key role in ICM growth and to be the major driver behind these differences.

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Two ICMs within the same blastocyst were at different stages of development

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IGF1-mediated signaling is likely to be the major driver behind these differences

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The expression pattern of YAP1 is different in human embryos from in the mouse

Cord Occlusion in Monochorionic Twins with Early Selective Intrauterine Growth Restriction and Abnormal Umbilical Artery Doppler: A Consecutive Series of 90 Cases

Objective: To describe perinatal outcomes achieved with cord occlusion (CO) in monochorionic twins with severe selective intrauterine growth restriction (sIUGR) and abnormal umbilical artery Doppler in the IUGR twin (types II and III). Methods: We studied a consecutive series of 90 cases of sIUGR with abnormal Doppler treated with CO of the IUGR fetus. Abnormal Doppler was defined as continuous (type II, n = 41) or intermittent (type III, n = 49) absent/reversed end-diastolic flow. All cases presented at least one of the following severity criteria: gestational age (GA) <22 weeks, inter-twin estimated weight discordance >35%, reversed end-diastolic umbilical artery flow or ductus venosus pulsatility index >95th centile. We prospectively recorded pregnancy course and perinatal outcome. Results: Median GA at surgery was 20.6 weeks and mean duration 22.4 min. Miscarriage (<24 weeks) occurred in 3.3% (3/90) and preterm delivery <32 weeks in 7.1% (6/84) of continuing pregnancies. GA at delivery was 36.4 weeks and neonatal survival of the larger twin was achieved in 93.3%. Conclusion: In a consecutive series studied by an experienced team, CO in monochorionic twins with severe sIUGR type II or III was associated with delivery >32 weeks in 92.9% and neonatal survival of the normal twin in 93.3% of pregnancies.

The impact of chorionicity on maternal pregnancy outcomes

OBJECTIVE

Women carrying twin pregnancies often receive similar counseling, regardless of chorionicity, with the notable exception of twin-twin transfusion syndrome (TTTS); however, little is known about whether the presence of 1 vs 2 placentas confers dissimilar maternal risks. We sought to determine differences in maternal and neonatal outcomes based on chorionicity.

STUDY DESIGN

This was a retrospective cohort study of all twin pregnancies at our institution undergoing routine second-trimester ultrasound for anatomic survey from 1990 through 2010. Secondary outcomes included other adverse maternal and neonatal outcomes. Relative risks and adjusted odds ratios (aORs) were calculated. Cluster analysis was used to account for nonindependence of twin pairs.

RESULTS

Of 2301 pregnancies, 1747 (75.9%) were dichorionic and 554 (24.1%) were monochorionic. Rates of preeclampsia, gestational diabetes, placental abruption, placenta previa, preterm labor, and preterm premature rupture of membranes (PPROM) were not significantly different in dichorionic vs monochorionic pregnancies. Early preterm delivery less than 34 weeks (aOR, 1.47; 95% confidence interval [CI], 1.17-1.86) and less than 28 weeks (aOR, 2.58; 95% CI, 1.58-4.20) were more likely in monochorionic twins, as was neonatal intensive care unit admission (aOR, 1.41; 95% CI, 1.12-1.78). Monochorionic twins delivered earlier at a mean gestational age of 34.2 weeks vs 35.0 weeks for dichorionic twins (P < .001). Hospital length of stay was significantly longer for monochorionic twins with a mean of 13.7 days vs 10.8 days for dichorionic twins (P = .01).

CONCLUSION

There are no significant differences in maternal outcomes by chorionicity; however, monochorionicity is associated with increased fetal risks. This information may be helpful in guiding more targeted counseling to expectant parents of twins that, although the presence of an additional placenta does not confer additional maternal risks, monochorionic infants tend to deliver earlier and require longer hospital stays.

Discordance in fetal biometry and Doppler are independent predictors of the risk of perinatal loss in twin pregnancies

OBJECTIVE

Impaired fetal growth might be better evaluated in twin pregnancies by assessing the intertwin discordance rather than the individual fetal size. The aim of this study was to investigate the prediction of perinatal loss in twin pregnancy using discordance in fetal biometry and Doppler.

STUDY DESIGN

This was a retrospective cohort study in a tertiary referral center. The estimated fetal weight (EFW), umbilical artery (UA) pulsatility index (PI), middle cerebral artery (MCA) PI, cerebroplacental ratio (CPR), and their discordance recorded at the last ultrasound assessment before delivery or demise of one or both fetuses were converted into centiles or multiples of the median (MoM). The discordance was calculated as the larger value-smaller value/larger value. A logistic regression analysis was performed to identify, and adjust for, potential confounders. The predictive accuracy was assessed using receiver-operating characteristic curve analysis.

RESULTS

The analysis included 620 (464 dichorionic diamniotic and 156 monochorionic diamniotic) twin pregnancies (1240 fetuses). Perinatal loss of one or both fetuses complicated 16 pregnancies (2.6%). The combination of EFW discordance and CPR discordance had the best predictive performance (area under the curve, 0.96; 95% confidence interval, 0.92-1.00) for perinatal mortality. The detection rate, false-positive rate, positive likelihood ratio, and negative likelihood ratio were 87.5%, 6.7%, 13.08, and 0.13, respectively. The EFW centile, EFW below the 10th centile (small for gestational age), UA PI discordance, MCA PI discordance, and MCA PI MoM were significantly associated with the risk of perinatal loss on univariate analysis, but these associations became nonsignificant after adjusting for other confounders (P = .097, P = .090, P = .687, P = .360, and P = .074, respectively). The UA PI MoM, CPR MoM, EFW discordance, and CPR discordance were all independent predictors of the risk of perinatal loss, even after adjusting for potential confounders (P = .022, P = .002, P < .001, and P = .010, respectively).

CONCLUSION

EFW discordance and CPR discordance are independent predictors of the risk of perinatal loss in twin pregnancies. Their combination could identify the majority of twin pregnancies at risk of perinatal loss. These findings highlight the importance of discordance in Doppler indices of fetal hypoxia, as well as fetal size, in assessing the risk of perinatal mortality.

The North American Fetal Therapy Network Consensus Statement: prenatal management of uncomplicated monochorionic gestations

Owing to vascular connections within a single placenta, monochorionic gestations present distinctive prenatal management challenges. Complications that can arise as a result of unbalanced hemodynamic exchange (twin-twin transfusion syndrome and twin anemia polycythemia sequence) and unequal placental sharing (selective fetal growth restriction) should be kept in mind while prenatal management is being planned. Because of unique monochorionic angioarchitecture, what happens to one twin can directly affect the other. Death of one twin can result in death or permanent disability of the co-twin. Early detection of these unique disease processes through frequent ultrasonographic surveillance may allow the opportunity for earlier referral, intervention, or both and potentially better outcomes. Therefore, monochorionic gestations should be managed differently than dichorionic gestations or singletons. The purpose of this document is to present in detail methods for monitoring and management of uncomplicated monochorionic gestations and to review the evidence for the roles of these methods for detection of complications in clinical practice. Finally, we present evidence-based and expert opinion-supported recommendations developed by the North American Fetal Therapy Network for the diagnosis, surveillance, and delivery of uncomplicated monochorionic gestations.

The association of crown-rump length discrepancy with birthweight discordance in spontaneous versus IVF monochorionic twins: a multicenter study

OBJECTIVE

The objective of this study was to compare the associations of crown-rump length (CRL) discrepancy with birthweight discordance in spontaneous versus in vitro fertilization (IVF) monochorionic (MC) twin pregnancies.

METHOD

This is a multicenter retrospective study on women with twin pregnancies assessed for nuchal translucency between January 1997 and July 2013. The study group was subdivided into MC twins conceived spontaneously and after IVF. Pregnancies with later fetal death or twin transfusion syndrome were excluded. A large-weight discordance was defined as a difference of birthweights of >15%.

RESULTS

The study group included 171 pregnancies; of them, 142 (83%) were spontaneous and 29 (17%) were IVF conceived. In the entire cohort, we found a significant correlation between birthweight discordance and CRL discrepancy (r = 0.173, P < 0.05). While a significant correlation was found between CRL discrepancy and birthweight discordance in spontaneous-conceived pregnancies (n = 142, r = 0.24, P = 0.005), such correlation was not present in IVF pregnancies (n = 29, r = -0.7, P = 0.724). A logistic regression analysis found significant odds of larger-weight discordance for each increase of 1% in CRL discrepancy among spontaneously conceived pregnancies (odds ratio = 1.1, confidence interval = 1.03-1.2, P = 0.005). A receiver operating characteristic (ROC) for large-weight discordance in the spontaneously conceived pregnancies demonstrated an area under the ROC curve of 0.613 (P = 0.039).

CONCLUSION

The significant correlation between CRL discrepancy and birthweight discordance in spontaneous versus IVF MC twin pregnancies might suggest differential monozygotic twinning process.

Neonatal outcome of late preterm uncomplicated monochorionic twins: what is the optimal time for delivery?

OBJECTIVE

To determine the neonatal outcome at late prematurity of uncomplicated monochorionic (MC) twin pregnancies.

METHODS

A retrospective cohort study of 166 patients with uncomplicated MC diamniotic twins delivered between 34 and 37 weeks of gestation at a single tertiary center. The study population was classified into four groups according to the gestational age at delivery: (1) 34 weeks, (2) 35 weeks, (3) 36 weeks and (4) 37 weeks. Neonatal outcome measures were compared between the groups.

RESULTS

Neonatal morbidity was significantly higher at 34 weeks of gestation compared to the other three groups including respiratory distress syndrome, oxygen requirement, hypothermia and hyperbilirubinemia. Moreover, the rate of admission to the special care unit and need for phototherapy were significantly higher in newborns born at 36 weeks compared to 37 weeks of gestation (p = 0.02 and 0.03 respectively). Multiple regression analysis revealed that the risk for adverse neonatal outcome was significantly associated with gestational age at delivery. Of note, there were no fetal or neonatal deaths in our cohort.

CONCLUSIONS

The risk of neonatal morbidity of uncomplicated MC twins delivered at 34-37 weeks of gestation significantly decreases with advanced gestation. Therefore, under close fetal surveillance, uncomplicated MC twin pregnancies should be delivered at 37 weeks of gestation.

Doppler abnormalities in monochorionic diamniotic twin pregnancies with discordant growth

OBJECTIVE

We studied whether abnormal umbilical artery (UA) Doppler flow velocity waveforms occur with higher frequency in monochorionic diamniotic (MCDA) twin gestations with discordant fetal growth and whether this impacted neonatal outcome.

STUDY DESIGN

We performed a retrospective study of MCDA twin pairs. We collected data from an electronic medical record. We classified pregnancies as discordant if there was at least 20% birth weight discordance. Abnormal UA Doppler velocity waveforms included absent or reversed end diastolic flow. We analyzed the data with chi square, Student's t-test and analysis of variance as appropriate.

RESULT

Seventy-three twin pairs met criteria for inclusion, including 16 with discordant growth. The discordant group was significantly more affected with twin-to-twin transfusion syndrome (TTTS) (P=0.02). The smaller fetuses in discordant pairs were more likely to display abnormal UA Doppler flow velocity waveforms (P<0.01). These neonates also had lower Apgar scores (P=0.03) and were more likely to require care in a neonatal intensive care unit. Our findings persisted after excluding pregnancies with TTTS.

CONCLUSION

In MCDA twin gestations complicated by discordant growth, there is an increased frequency of abnormal UA Doppler flow velocity waveforms in small fetuses, and these neonates face clinical challenges after birth.

Neurodevelopmental outcome of twins at two years of age according to the planned mode of delivery

OBJECTIVES

To determine neurodevelopment at two years in twins.

METHODS

At two years of age, all twins ≥32 weeks, delivered in our center and not randomized in the Twin Birth Study, underwent a neurodevelopment screen using the Ages and Stages Questionnaire (ASQ). Children with ≥1 abnormal ASQ domain score were evaluated by a pediatrician. Results were documented according to a planned cesarean section (PCS) or a planned vaginal delivery (PVD).

RESULTS

An ASQ was obtained from 185 children (67%). No significant differences in percentages of abnormal scores were found between the PCS group and the PVD group or between twins A and B. Pediatric assessment revealed three children with a neurodevelopmental delay. Five other children were already under pediatric or general practitioner care for other reasons. One child with a congenital anomaly was born by a PCS, two twins A and five twins B were born in the PVD group.

CONCLUSION

ASQ screening revealed no significant differences in abnormal neurodevelopment in twins at two years of age according to the mode of delivery. Pediatric assessment suggested an increased incidence for abnormal neurodevelopment in twins B born by PVD.

Clinical factors affecting the timing of delivery in twin pregnancies

OBJECTIVE

To investigate clinical factors affecting the timing of delivery in twin pregnancies in order to minimize perinatal complications.

METHODS

A retrospective study involved 163 twin pregnancies delivered from January 2006 to September 2011 at Gachon University Gil Medical Center. These cases were divided into three groups based on the delivery timing: less than 32 weeks' gestation (group A), between 32 and 35+6 weeks' gestation (group B), and over 36 weeks' gestation (group C). Clinical factors including maternal age, parity, presence of premature uterine contraction, presence of premature rupture of membrane, white blood cell, high sensitive C-reactive protein level, cervical dilatation, maternal complication, chorionicity, twin specific complication, and perinatal complication were analyzed for each group.

RESULTS

In group B, the timing of delivery was postponed for 14 days or more from the time of admission, and there were fewer numbers of babies with low Apgar score at birth compared with other groups. The frequency of uterine contraction (P<0.001), presence of premature rupture of membranes (P=0.017), dilatation of cervix (P<0.001), increased white blood cell and high sensitive C-reactive protein levels (P=0.002, P<0.001) were important clinical factors during decision making process of delivery timing in twin pregnancies. Twin specific fetal conditions, such as twin-twin transfusion syndrome and discordant growth (over 25% or more) were shown more frequently in group A. However, there were no significant statistical differences among three groups (P=0.06, P=0.14).

CONCLUSION

Proper management for preventing premature contraction and inflammation can be essential in twin pregnancies until 32 weeks' gestation, and may decrease maternal and perinatal complications.

An analysis of pregnancy outcome in dichorionic and monochorionic twins given special antenatal and intranatal care: a four-year survey

OBJECTIVE

The present study aims to analyze perinatal outcomes in twins given special care during pregnancy and labor and to compare fetal and neonatal outcomes in dichorionic twins with monochorionic twins.

STUDY DESIGN

Eighty eight (88) twin pregnancies booked for care at a tertiary care Fetal Medicine centre were included in this study. The maternal demographic variables, course of pregnancy, fetal problems, and specialized fetal therapeutic and diagnostic interventions were noted. The above parameters were compared in the sub-groups of dichorionic and monochorionic twin pregnancies and related to the perinatal outcome. Statistical analysis was done using the student's t test and the two-tailed chi sqaure tests with Yate's continuity correction. A p value <0.05 was considered as significant.

RESULTS

Mean maternal age was 30.34 + 4.81 years (range 19-48). 81 % of the twins were DCDA, and 19 % were MCDA. The mean gestational age at delivery was 34.4 ± 3.5 weeks, and this was not significantly different in MCDA and DCDA groups. Serious fetal problems warranting intervention at the time of initial referral were significantly higher in MCDA twins although overall perinatal outcome in both groups were not different.

CONCLUSION

Specialized care during pregnancy and labor including active fetal surveillance and therapeutic intervention when indicated improves the perinatal outcome in twin pregnancies and ensured at least one healthy live birth in over 90 % cases, although with an increase in late prematurity.

Crown-rump length discordance in the first trimester: a predictor of adverse outcome in twin pregnancies?

OBJECTIVES

To evaluate the usefulness of first-trimester crown-rump length (CRL) discordance in predicting adverse outcome in twin pregnancies.

METHODS

This retrospective study included a large cohort retrieved from local ultrasound databases at 14 obstetric departments in Denmark, comprising all twin pregnancies with two live fetuses scanned between 11 and 14 weeks' gestation during the period 1 January 2004 to 31 December 2006. The association between CRL discordance ≥ 10 % and adverse outcome was evaluated.

RESULTS

Among 1993 twin pregnancies, 1733 were dichorionic (156 (9%) discordant; 1577 (91%) concordant) and 260 were monochorionic (32 (12%) discordant; 228 (88%) concordant). In dichorionic twin pregnancies we found an association between CRL discordance ≥ 10% and preterm delivery before 34 weeks' gestation (P=0.007), birth weight discordance (P=0.001) and mean birth weight (P=0.033). In monochorionic twin pregnancies we found an association between CRL discordance ≥ 10% and birth weight discordance (P=0.02) and mean birth weight (P=0.03). To evaluate CRL discordance as a predictor of fetal loss and preterm delivery before 34 weeks' gestation, receiver-operating characteristics curves were created for each outcome. For CRL discordance ≥ 10% as a predictor of fetal loss and preterm delivery in dichorionic twin pregnancies, sensitivity was 0.17 (95% CI, 0.06-0.28) and 0.14 (95% CI, 0.10-0.18), respectively, and in monochorionic twin pregnancies it was 0.10 (95% CI, 0.03-0.22) and 0.16 (95% CI, 0.06-0.26), respectively.

CONCLUSIONS

CRL discordance in twin pregnancies is associated with, but is not a strong predictor of, adverse outcome.

First-trimester sonographic prediction of obstetric and neonatal outcomes in monochorionic diamniotic twin pregnancies

OBJECTIVES

The purpose of this study was to investigate whether discordant nuchal translucency and crown-rump length measurements in monochorionic diamniotic twins are predictive of adverse obstetric and neonatal outcomes.

METHODS

We conducted a multicenter retrospective cohort study including all monochorionic diamniotic twin pregnancies with two live fetuses at the 11-week to 13-week 6-day sonographic examination who had serial follow-up sonography until delivery. Isolated nuchal translucency, crown-rump length, and combined discordances were correlated with adverse obstetric outcomes, individually and in composite, including the occurrence of 1 or more of the following in either fetus: intrauterine growth restriction (IUGR), twin-twin transfusion syndrome (TTTS), intrauterine fetal death (IUFD), growth discordance (≥ 20%), and preterm birth before 28 weeks' gestation. Correlations with adverse composite neonatal outcomes were also studied. A receiver operating characteristic curve analysis and a logistic regression analysis with a generalized estimating equation were conducted.

RESULTS

Fifty-four of the 177 pregnancies included (31%) had an adverse composite obstetric outcome, with TTTS in 19 (11%), IUGR in 21 (12%), discordant growth in 14 (8%), IUFD in 14 (8%), and preterm birth before 28 weeks in 10 (6%). Of the 254 neonates included in the study, 69 (27%) were complicated by adverse composite neonatal outcomes, with respiratory distress syndrome being the most common (n = 59 [23%]). The areas under the curve for the combined discordances to predict composite obstetric and neonatal outcomes were 0.62 (95% confidence interval, 0.52-0.72), and 0.54 (95% confidence interval, 0.46-0.61), respectively.

CONCLUSIONS

In our population, nuchal translucency, crown-rump length, and combined discordances in monochorionic diamniotic twin pregnancies were not predictive of adverse composite obstetric and neonatal outcomes.

Prospective study of the MD-twin score for antepartum evaluation of monochorionic diamniotic twins and its correlation with perinatal outcomes

AIM

To assess the outcome of monochorionic diamniotic (MD) twins with the aid of the MD-twin score.

METHODS

We enrolled 112 MD-twin women in a tertiary perinatal center from 1997 to 2009. The MD-twin score was prospectively applied once per week to women who did not have twin-to-twin transfusion syndrome (TTTS) after 26 weeks of gestation. The MD-twin score consists of five variables: (i) fetal weight discordance; (ii) amniotic fluid discordance; (iii) hydrops fetalis; (iv) umbilical cord insertion; and (v) fetal heart rate monitoring. Normal was assigned a value of 0, abnormal was assigned 1, and total score was used for evaluation. Women with scores of 2 at 26 weeks gestation were managed expectantly until the score reached 3. Outcome measures were fetal death, neonatal death and neurological sequelae. The incidence of poor outcome according to score was investigated. The characteristics of MD twins with poor outcome were investigated.

RESULTS

MD-twin scores were applied to 90 women. Among them, 79 had scores of 2 or less and all had good outcomes. There were 11 women with a score of 3, four of whom had adverse outcome for at least one twin. Neonates born to women with scores of 0-2 had good outcomes without respect to birthweight percentile, while neonates with scores of 3 had poor outcomes when their birthweight percentile was less than the third percentile.

CONCLUSION

The MD-twin score is applicable to 90% of MD twins without TTTS. An MD-twin score of 2 is reassuring, while a score of 3 indicates increased risks for adverse outcome.

Perinatal complications of monochorionic diamniotic twin gestations with discordant crown-rump length determined at mid-first trimester

AIM

The aim of this study was to investigate the value of discordance of crown-rump length (DCRL) at mid-first trimester to predict adverse outcomes in monochorionic diamniotic twin gestations (MD).

MATERIAL AND METHODS

This was a retrospective cohort study of the perinatal outcome in MD pregnancies managed from the first trimester onward. DCRL was evaluated between 8 and 10 weeks of gestation. The association between DCRL and perinatal complications, including fetal death, twin-twin transfusion syndrome, severe discordant birthweight (DB), and twin anemia-polycythemia sequence, was assessed.

RESULTS

Among 126 cases, a single fetal demise occurred in two (2%) and demise of both fetuses occurred in eight (6%). Five pregnancies (4%) were complicated with twin-twin transfusion syndrome; one case (1%) was twin anemia-polycythemia sequence and 13 (10%) were DB. Neonatal death occurred in one pair. At 28 days of age, in 115 cases (91%) both twins were alive. In 117 cases (93%), at least one twin survived until 28 days of age. DCRL >12.0% was not related to any perinatal complications but DB (P < 0.01; relative risk: 1.40; 95% confidence interval: 1.06-1.84).

CONCLUSIONS

DCRL in MD during the mid-first trimester might be useful for predicting DB.

[Perinatal outcome of monochorionic and dichorionic twin gestations: a study of 775 pregnancies at Reunion Island]

OBJECTIVES

To compare the perinatal mortality and morbidity of infants born from monochorionic versus dichorionic twin pregnancies (TP).

PATIENTS AND METHODS

Retrospective, comparative study of monochorionic and dichorionic TP over 10 years in the south of Reunion Island. Information regarding demographic, gestational and perinatal variables of mothers and infants was collected from the hospital perinatal database.

RESULTS

Six hundred and twenty dichorionic and 155 monochorionic TP were analyzed. In case of monochorionic TP, mothers had higher rates of pregnancy-related hypertension (OR=1.82, 95%CI=[1.02-3.29] ; P=0.03) and hospitalization (OR=1.48, 95%CI=[1.02-2.16]; P=0.03). Newborns from monochorionic TP had higher morbidity for : very preterm birth (birth before 33 weeks gestation) (OR=1.65, 95%CI=[1.02-2.66]; P=0.02), very low birth weight (birth weight<1500g) (OR=1.73, 95%CI=[1.57-3.13]; P<0.001), Apgar<7 at 1 minute (OR=1.76, 95%CI=[1.18-2.61]; P<0.01) and hospitalization (OR=2.08, 95%CI=[1.58-2.73]; P<0.001). Perinatal mortality was also significantly higher (OR=2.47, 95%CI=[1.54-3.94]; P<0.001), as well intrauterine fetal death (OR=3.96, 95%CI=[1.95-8.05]; P<0.001) CONCLUSION: This study confirms that few differences exist among dichorionic and monochorionic TP with regard to maternal morbidity, while neonatal morbidity and mortality are higher in twins born from monochorionic pregnancies.

Prematurity and twinning

AIM OF THE STUDY

Newborns from multiple pregnancies are increasing in number and demonstrate a higher perinatal morbidity and mortality compared to singletons. Prematurity is the main reason for most neonatal diseases in twins, but other variables may play a role and their prenatal evaluation may improve the overall outcome.

MAIN FINDINGS

Prematurity is six times more frequent in twins and therefore birth weight is significantly lower compared to singletons. Thus, twins are more exposed to prematurity related diseases (respiratory, cardiovascular, infectious, etc.) and to long-term complications (especially neurological disabilities).

RESULTS

It is very difficult to estimate the increased risk of neonatal morbidity related to twinning independently to the increased risk of prematurity and therefore to interpret data on morbidity rates, in particular regarding the neurodevelopmental outcome.

CONCLUSION

Prevention of preterm birth is a primary goal in managing multiple pregnancies, together with prophylaxis with corticosteroids in order to improve foetal lung maturity. Accurate risk assessment strategies and adequate obstetrical-neonatological management of multiple pregnancies may reduce the increasing need for neonatal intensive care and for health resources in the long-term follow-up that has been observed over the last decades.

Mitochondrial activation in the growth-restricted fetus of monochorionic twins

OBJECTIVE

To study the regulatory mechanisms of selective intrauterine growth restriction (sIUGR) independent of confounding genetic factors, monochorionic (MC) twins are the ideal model, because they have identical genomic DNA. We hypothesize that the intrauterine growth restriction fetus has mitochondrial activation compared with its larger counterpart, and sought to demonstrate this using the MC twin model.

DESIGN

Fetal cord blood and amniotic fluid of MC twins were prospectively collected during delivery. Mitochondrial DNA of cord blood was measured using real-time quantitative polymerase chain reaction (PCR), and mitochondria in amniotic fluid mesenchymal stem cells (AFMSCs) were analyzed with MitoTracker staining.

SETTING

Tertiary referring center.

PATIENT(S)

Forty-three pairs of MC twins, including 24 pairs with sIUGR and 19 pairs without.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Mitochondrial DNA contents were measured and presented as fold difference between the small and large fetuses. After staining with MitoTracker, mitochondrial intensity in AFMSCs was analyzed with the Image J program.

RESULT(S)

The fold differences of the cord blood mitochondrial DNA content between the small and large twins were significantly higher in the MC twins with sIGUR (2.5 ± 1.2, n = 24 pairs) than in those without sIUGR (1.2 ± 0.3, n = 19 pairs). In addition, mitochondrial staining intensities were significantly higher in the AFMSCs derived from growth-restricted fetuses than from control fetuses.

CONCLUSION(S)

Mitochondrial activation in the sIUGR fetus of MC twins was likely regulated by locally adverse placental and blood flow conditions, instead of genetic factors.

[Pediatric outcome after selective feticide for 30 complicated monochorionic twin pregnancies]

OBJECTIVES

To describe perinatal and pediatric outcome after selective feticide for complicated monochorionic twin pregnancy.

PATIENTS AND METHODS

We reviewed all consecutive cases of umbilical cord occlusion performed for complicated monochorionic twin pregnancy over a 16-year period. Pediatric follow-up was based on medical records and updated by phone calls to the parents.

RESULTS

Thirty procedures were performed. Indications were: twin-to-twin transfusion syndrome (TTTS) progressing despite serial amniodrainage (n=12) ; twin reversed arterial perfusion (n=9) ; selective growth restriction (n=5) ; severe discordant structural anomalies (n=4). Mean gestational age at procedure was 21.8±3.1gestational weeks (GW) and 31.8±4.8 GW at birth. Overall survival rate was 87%, i.e. 83%, 100%, 60% and 100% for each indication, respectively. Mean pediatric follow-up was 5years (range: 6months to 15years). Medical charts and parents declared normal development in 88% of surviving children, i.e. 67%, 100%, 100%, and 100% for each indication. Cross-comparison between the four groups revealed that in the TTTS group, gestational age at procedure was more advanced (P=0.01) while delivery was slightly earlier (P=0.1), and pediatric development was poorer (P=0.02).

DISCUSSION AND CONCLUSION

Pediatric outcome after selective feticide appeared to be poorer for TTTS progressing despite serial amniodrainage than for other indications.

The vascular anastomoses in monochorionic twin pregnancies and their clinical consequences

Monochorionic twin pregnancies are at increased risk of adverse outcome because of the vascular anastomoses that connect the 2 fetal circulation systems. The shared circulation is responsible for some unique complications in monochorionic twins, such as the twin-to-twin transfusion syndrome, the twin anemia polycythemia sequence, the twin reversed arterial perfusion sequence, and monoamniotic twinning. Another consequence of the shared circulation is that the well-being of one twin critically depends on that of the other. In this review, we will describe the technique of placental injection. Further, we will discuss the role of the vascular anastomoses in each of the complications described above and provide an update on their management.

Twin-twin transfusion syndrome

OBJECTIVE

We sought to review the natural history, pathophysiology, diagnosis, and treatment options for twin-twin transfusion syndrome (TTTS).

METHODS

A systematic review was performed using MEDLINE database, PubMed, EMBASE, and Cochrane Library. The search was restricted to English-language articles published from 1966 through July 2012. Priority was given to articles reporting original research, in particular randomized controlled trials, although review articles and commentaries also were consulted. Abstracts of research presented at symposia and scientific conferences were not considered adequate for inclusion in this document. Evidence reports and guidelines published by organizations or institutions such as the National Institutes of Health, Agency for Health Research and Quality, American College of Obstetricians and Gynecologists, and Society for Maternal-Fetal Medicine were also reviewed, and additional studies were located by reviewing bibliographies of identified articles. Consistent with US Preventive Task Force guidelines, references were evaluated for quality based on the highest level of evidence, and recommendations were graded accordingly.

RESULTS AND RECOMMENDATIONS

TTTS is a serious condition that can complicate 8-10% of twin pregnancies with monochorionic diamniotic (MCDA) placentation. The diagnosis of TTTS requires 2 criteria: (1) the presence of a MCDA pregnancy; and (2) the presence of oligohydramnios (defined as a maximal vertical pocket of <2 cm) in one sac, and of polyhydramnios (a maximal vertical pocket of >8 cm) in the other sac. The Quintero staging system appears to be a useful tool for describing the severity of TTTS in a standardized fashion. Serial sonographic evaluation should be considered for all twins with MCDA placentation, usually beginning at around 16 weeks and continuing about every 2 weeks until delivery. Screening for congenital heart disease is warranted in all monochorionic twins, in particular those complicated by TTTS. Extensive counseling should be provided to patients with pregnancies complicated by TTTS including natural history of the disease, as well as management options and their risks and benefits. The natural history of stage I TTTS is that more than three-fourths of cases remain stable or regress without invasive intervention, with perinatal survival of about 86%. Therefore, many patients with stage I TTTS may often be managed expectantly. The natural history of advanced (eg, stage ≥III) TTTS is bleak, with a reported perinatal loss rate of 70-100%, particularly when it presents <26 weeks. Fetoscopic laser photocoagulation of placental anastomoses is considered by most experts to be the best available approach for stages II, III, and IV TTTS in continuing pregnancies at <26 weeks, but the metaanalysis data show no significant survival benefit, and the long-term neurologic outcomes in the Eurofetus trial were not different than in nonlaser-treated controls. Even laser-treated TTTS is associated with a perinatal mortality rate of 30-50%, and a 5-20% chance of long-term neurologic handicap. Steroids for fetal maturation should be considered at 24 0/7 to 33 6/7 weeks, particularly in pregnancies complicated by stage ≥III TTTS, and those undergoing invasive interventions.

Behavior genetics and postgenomics

The science of genetics is undergoing a paradigm shift. Recent discoveries, including the activity of retrotransposons, the extent of copy number variations, somatic and chromosomal mosaicism, and the nature of the epigenome as a regulator of DNA expressivity, are challenging a series of dogmas concerning the nature of the genome and the relationship between genotype and phenotype. According to three widely held dogmas, DNA is the unchanging template of heredity, is identical in all the cells and tissues of the body, and is the sole agent of inheritance. Rather than being an unchanging template, DNA appears subject to a good deal of environmentally induced change. Instead of identical DNA in all the cells of the body, somatic mosaicism appears to be the normal human condition. And DNA can no longer be considered the sole agent of inheritance. We now know that the epigenome, which regulates gene expressivity, can be inherited via the germline. These developments are particularly significant for behavior genetics for at least three reasons: First, epigenetic regulation, DNA variability, and somatic mosaicism appear to be particularly prevalent in the human brain and probably are involved in much of human behavior; second, they have important implications for the validity of heritability and gene association studies, the methodologies that largely define the discipline of behavior genetics; and third, they appear to play a critical role in development during the perinatal period and, in particular, in enabling phenotypic plasticity in offspring. I examine one of the central claims to emerge from the use of heritability studies in the behavioral sciences, the principle of minimal shared maternal effects, in light of the growing awareness that the maternal perinatal environment is a critical venue for the exercise of adaptive phenotypic plasticity. This consideration has important implications for both developmental and evolutionary biology.

Genetic, environmental and stochastic factors in monozygotic twin discordance with a focus on epigenetic differences

Genetic-epidemiological studies on monozygotic (MZ) twins have been used for decades to tease out the relative contributions of genes and the environment to a trait. Phenotypic discordance in MZ twins has traditionally been ascribed to non-shared environmental factors acting after birth, however recent data indicate that this explanation is far too simple. In this paper, we review other reasons for discordance, including differences in the in utero environment, genetic mosaicism, and stochastic factors, focusing particularly on epigenetic discordance. Epigenetic differences are gaining increasing recognition. Although it is clear that in specific cases epigenetic alterations provide a causal factor in disease etiology, the overall significance of epigenetics in twin discordance remains unclear. It is also challenging to determine the causality and relative contributions of environmental, genetic, and stochastic factors to epigenetic variability. Epigenomic profiling studies have recently shed more light on the dynamics of temporal methylation change and methylome heritability, yet have not given a definite answer regarding their relevance to disease, because of limitations in establishing causality. Here, we explore the subject of epigenetics as another component in human phenotypic variability and its links to disease focusing particularly on evidence from MZ twin studies.

Placenta Share Discordance and Umbilical Artery Doppler Change After Antenatal Betamethasone Administration in Monochorionic Twins With Selective Intrauterine Growth Restriction: Is There a Link?

This study was designed to evaluate the degree of placenta share discordance in relation to the betamethasone-induced return of positive end-diastolic flow in monochorionic twin pregnancies with selective intrauterine growth restriction (sIUGR) and abnormal umbilical artery Doppler. Monochorionic twins with sIUGR was defined as one twin having an estimated fetal weight below the 10th percentile combined with an estimated fetal weight discordance >25%. The umbilical artery Doppler directly prior to (D0) and 24 hours (D1) and 48 hours (D2) after the first dose of betamethasone administration was recorded. The estimated individual placental weight in monochorionic twins was obtained by cutting the placenta along the vascular equator into two territories; the placenta share discordance was calculated as [(estimated individual placental weight of appropriated for gestational age twin- estimated individual placental weight of growth restricted twin)/estimated individual placental weight of appropriated for gestational age twin] × 100%. Six (23.1%) of the 26 included cases achieved betamethasone-induced return of positive umbilical artery end-diastolic flow. The difference of placenta share discordance and birth weight discordance were not significantly different between twins with and without betamethasone-induced return of positive umbilical artery end-diastolic flow. Thus, according to our study results, it was proposed that although the placenta share discordance correlated with the abnormal umbilical artery Doppler in the IUGR fetus in monochorionic twin, the betamethasone-induced return of positive umbilical artery end-diastolic flow, however, did not reveal the similar relationship with the severity of placenta share discordance.

Successful in utero treatment of an oral teratoma via operative fetoscopy: case report and review of the literature

The prenatal diagnosis of a nasopharyngeal teratoma carries a very grave prognosis. Although these tumors constitute only 9% of all teratomas, all previous cases diagnosed antenatally have been associated with either fetal demise or emergent surgery at birth. Of the fetuses that survive to birth, delivery can be associated with airway obstruction and multiple postnatal surgeries. These complications could be averted if the tumor could be safely treated in utero. We hereby report the successful treatment of an oral teratoma via operative fetoscopy, with the birth of a healthy infant at term.

Effectiveness of timing strategies for delivery of monochorionic diamniotic twins

OBJECTIVE

The purpose of this study was to compare strategies for delivery timing of uncomplicated monochorionic diamniotic twin pregnancies.

STUDY DESIGN

A decision tree compared 9 strategies that included scheduled delivery between 32 and 38 weeks' gestation, with or without confirmation of fetal lung maturity. Outcomes in the model included fetal death, infant death, respiratory distress syndrome, mental retardation, and cerebral palsy.

RESULTS

A scheduled delivery at 38 weeks' gestation was the preferred strategy, which resulted in the highest quality adjusted life years under base-case assumptions. Decreased, but comparable, quality adjusted life years estimates resulted from scheduled deliveries at 36 and 37 weeks' gestation, with or without amniocentesis. Sensitivity analyses demonstrated that the optimal gestational age for delivery was always ≥36 weeks' gestation.

CONCLUSION

This decision analysis suggests that, for women with uncomplicated monochorionic twins, delivery between 36 and 38 weeks' gestation is the preferred strategy for timing of delivery.

The Relationships of Umbilical Venous Volume Flow, Birthweight and Placental Share in Monochorionic Twin Pregnancies With and Without Selective Intrauterine Growth Restriction

This study was conducted to investigate the relationship among umbilical venous volume flow, birthweight and placental share in monochorionic twins with or without selective growth restriction. Having excluded cases complicated with twin-to-twin transfusion syndrome and one co-twin suffering intrauterine fetal death, a total of 51 monochorionic twin pregnancies were divided into two groups as with (group 1) and without (group 2) selective intrauterine growth restriction. Umbilical venous volume flow was calculated by multiplying the umbilical vein cross-sectional area by half of the maximal velocity around mid-trimester. The placentas were cut along the vascular equator into two individual placental masses. The discordance of birthweight was calculated as [(birthweight of larger twin—birthweight of smaller twin)/birthweight of larger twin 100%]. The discordances of umbilical venous volume flow and placental share were calculated in a similar fashion. The median umbilical venous volume flow discordances (68.4% and 15.3% in groups 1 and 2 monochorionic twins, respectively) were similar and correlated well with the placental share discordances (66.6% and 18.5% in groups 1 and 2 monochorionic twins, respectively) but not with the birthweight discordance (28.6% and 6.4% in groups 1 and 2 monochorionic twins, respectively) in both groups. We concluded that the umbilical venous volume flow discordance reflects the placental share discordance rather than the birthweight discordance in monochorionic twin pregnancies.