Management of twin pregnancies discordant for anencephaly

Objective To examine options of management and outcome of twin pregnancies discordant for anencephaly.
Design Retrospective study.
Setting Research Centre for Fetal Medicine.
Population Twenty-four twin pregnancies discordant for anencephaly.
Methods A computer search was made of our database for twin pregnancies discordant for anencephaly. The data were reviewed for gestation at presentation, chorionicity, management and pregnancy outcome.
Main outcome measures Pregnancy outcome in relation to chorionicity and management.
Results There were 13 dichorionic and 11 monochorionic twin pregnancies discordant for anencephaly. In the dichorionic group five pregnancies had selective fetocide at 17 to 21 weeks; one pregnancy resulted in spontaneous abortion but in the others a healthy infant was born at a median gestation of 37 weeks. The other eight dichorionic pregnancies were managed expectantly, but three developed polyhydramios at 26 to 30 weeks; in one case amniodrainage was performed and in another selective fetocide was carried out. In this group the median gestation at delivery was 35 weeks. All 11 monochorionic pregnancies were managed expectantly and in three there was intrauterine death of both fetuses. In the other eight cases the normal twin was liveborn at a median gestation of 34 weeks; in four of these pregnancies polyhydramnios developed and two were managed by amniodrainage.
Conclusions In monochorionic pregnancies, expectant management is associated with a high rate of intrauterine lethality of the normal twin. In dichorionic pregnancies selective fetocide in the second trimester prevents the development of polyhydramnios and is associated with a lower risk of preterm delivery but can cause miscarriage.     

Significance of twin to twin transfusion syndrome in the prognosis of twin pregnancies and its prenatal diagnosis by ultrasonography

The reason why TTS worsen the prognosis of twin pregnancies was discussed with reference to case results for perinatal death, and antenatal diagnostic criteria for TTS by ultrasonography was established. Of 12 perinatal deaths in 71 twin pregnancies, eight fetuses were affected with TTS (1 acardia, 4 donors, 3 recipients). Perinatal mortality rate (39.3%), rate of preterm lobar (62.2%), rate of polyhydramnion (50.0%), mean amniotic fluid volume (3.310 ml) and cord cross section area ratio (2.38) in monochorionic discordant twins were higher than in the other three groups (monochorionic concordant twins, dichorionic discordant twins and dichorionic concordant twins). Eight fetuses among 12 monochorionic discordant twins were affected with TTS. All twins which showed a single GS in early pregnancy were monochorionic twins. Therefore TTS was considered to have a poorer prognosis than usually reported for all TTS, and to find monochorionic discordant twins with a high cord cross section area ratio must be the key in the screening of TTS. Antenatal diagnosis of TTS by ultrasonography is summarized as follows: 1) A single GS in early pregnancy. 2) Estimated body weight difference between the twins/estimated body weight of the larger twins greater than or equal to 0.2. 3) Cord cross sectional area ratio greater than or equal to 2.0.     

Perinatal outcome, placental pathology, and severity of discordance in monochorionic and dichorionic twins

OBJECTIVE: To evaluate differences in pregnancy outcomes and placental findings among severely discordant monochorionic and dichorionic twins. METHODS: We studied retrospectively a cohort of 382 twin pregnancies with gestational ages that ranged from 24 to 40 weeks. Pregnancies were classified as dichorionic or monochorionic by histologic examination of placentas. Infants were subdivided into concordant (less than 5% difference in birth weight), mildly discordant (5-25% difference), and severely discordant groups (more than 25% difference), and their clinical characteristics and findings at placental examination were analyzed and compared. RESULTS: Severe discordance occurred significantly more often in monochorionic than in dichorionic twins and was associated with significantly more deliveries before 36 weeks and more newborns remaining more than 10 days in the neonatal intensive care unit. Severely discordant monochorionic and dichorionic twins had significantly worse perinatal mortality and morbidity than mildly discordant and concordant twins. The weight of the placenta of the smaller fetus in severely discordant dichorionic twins with separate placentas and the total placental weight in severely discordant monochorionic twins were significantly smaller than the weights of the placentas in their concordant and mildly discordant counterparts. The umbilical cords of the smaller fetuses in both dichorionic and monochorionic pregnancies exhibited significantly more velamentous insertions and single umbilical arteries than in concordant or mildly discordant twins of similar chorionicity. CONCLUSION: Severe discordance is more frequent and has greater morbidity in monochorionic than dichorionic twins. The most frequent findings in the placentas of severely discordant twins were small placental weight and umbilical cord abnormalities.     

Does chorionicity or zygosity predict adverse perinatal outcomes in twins?

OBJECTIVE: The purpose of this study was to evaluate chorionicity and zygosity as risk factors for adverse perinatal outcomes in twins. STUDY DESIGN: A population-based, retrospective cohort study was conducted of all twin deliveries in Nova Scotia, Canada, from 1988 to 1997. Chorionicity was established by histologic examination. Zygosity was determined by chorionicity, sex, and infant blood group. Three groups were established: monochorionic/monozygotic twins, dichorionic/dizygotic twins, and dichorionic/majority monozygotic twins. RESULTS: Outcomes from 1008 twin pregnancies were analyzed. Monochorionic/monozygotic twins had lower mean birth weights compared with dichorionic/dizygotic twins. Rates of perinatal mortality of at least 1 twin were significantly higher among monochorionic/monozygotic twins relative to dichorionic/dizygotic twins (relative risk, 2.5; 95% CI, 1.1-2.5). Dichorionic/majority monozygotic twins had similar perinatal outcomes compared with dichorionic/dizygotic twins. CONCLUSION: Monochorionicity increases the risk of adverse perinatal outcome, whereas the effect of zygosity is less clear. Because chorionicity can be determined by prenatal ultrasound scanning, this information should be considered in the prenatal care of twin pregnancies.     

Growth pattern of twins of different chorionicity evaluated by sonographic biometry

OBJECTIVE: To determine differences between growth patterns of monochorionic and dichorionic twins, and of concordant and discordant twins of both chorionicities. METHODS: We studied 70 cases of concordant twins (24 monochorionic, 46 dichorionic) and 45 cases of discordant twins (25 monochorionic, 20 dichorionic). In each case, growth was measured longitudinally by ultrasound biometry and the growth pattern was depicted. RESULTS: There were no differences in incremental growth between concordant monochorionic and dichorionic twins. The growth curve of concordant twins of both chorionicities was almost the same as that of a singleton until 34 weeks' gestation. However, in the discordant twins, the growth of the larger twin matched the growth curve of a singleton or concordant twin, but the growth of the smaller twin gradually decreased to the range of growth restriction. The growth curves for monochorionic discordant twins appeared to be representative of two groups, one of which had onset of discordancy before 24 weeks.CONCLUSION: It is clinically important to determine chorionicity early in twin pregnancies, to calculate the percentage of discordancy between the fetuses, and to examine longitudinal fetal growth curves in each chorionicity.     

Perinatal mortality in twin pregnancies: a 3-year analysis in Seine Saint-Denis (France).

OBJECTIVES: Our purpose was to evaluate perinatal mortality in twins and to investigate factors associated with this mortality. STUDY DESIGN: A prospective study on the perinatal mortality was performed in the department of Seine-Saint-Denis. Out of all the perinatal deaths, we have retrospectively isolated those arising from twin pregnancies. RESULTS: There were 54 twin pregnancies complicated with perinatal death. The perinatal mortality rate in twin pregnancy was 78.0 per 1000 twin babies delivered. Out of 86 twin deaths, 38 (44.2%) were born before 28 weeks gestation and out of 82 twin perinatal deaths, 37 (45.1%) weighed less than 1000 g. Chorionicity was recorded in 44 twin pairs: 21 (47.7%) were dichorionic and 23 (52.3%) monochorionic. Finally, out of 48 twin sets there were four (8.3%) monoamniotic pregnancies. CONCLUSIONS: The present data show that extreme prematurity represents nearly half of perinatal mortality in twins. This study indicates also a significant proportion of monochorionic placentation among twin pregnancies with poor outcome.     

Multiple pregnancy at 11+0 - 13+6 weeks

Chorionicity, rather than zygosity, is the main factor determining pregnancy outcome. In monochorionic twins the rates of miscarriage, perinatal death, preterm delivery, fetal growth restriction and fetal abnormalities are much higher than in dichorionic twins. High mortality confined to monochorionic pregnancies is the consequence of severe early-onset TTTS. Death of a monochorionic fetus is associated with a high chance of sudden death or severe neurological damage in the co-twin. Sonographic examination provides reliable distinction between dichorionic and monochorionic pregnancies. Reduction of the excess fetal loss in twins, can only be achieved through early identification of monochorionic pregnancies by ultrasound examination at 11+0 - 13+6 weeks, close surveillance and appropriate treatment in those that develop severe TTTS. In multiple pregnancies, compared to singletons, prenatal diagnosis of chromosomal abnormalities is complicated because, firstly, the techniques of invasive testing may provide uncertain results or may be associated with higher risks of miscarriage and, secondly, the fetuses may be discordant for an abnormality.     

Twin pregnancy outcome and chorionicity

BACKGROUND: Based on research of relatively poor quality, it is generally believed that dichorionic twins have lower perinatal mortality than monochorionic twins. We assessed the relationship between the pattern of perinatal loss in twin pregnancy and chorionicity. METHODS: A cohort study of 238 consecutive sets of twin pregnancies registered in our antenatal service over a 2-year period (1996-98) had chorionicity determined by ultrasound at 12-16 weeks' gestation. Follow up included scanning at 20 weeks' gestation for anomaly, and at 2-3-weekly intervals from 24 weeks' gestation onwards for growth and well being. Hazard ratios were computed for comparing the risk of death according to chorionicity. The perinatal loss patterns were analyzed according to gestational age at demize and that at delivery using survival analysis. RESULTS: Overall, 17/238 (7.1%) twin pregnancies suffered mortality: 14/190 (7.3%) amongst the dichorionic and 3/48 (6.2%) amongst the monochorionic twins. The hazard ratio for mortality was 0.89 (95% confidence interval 0.27-2.97, p = 0.85), considering gestational age at demize as the outcome. For gestational age at delivery as the outcome, the hazard ratio for mortality was 0.93 (95% confidence interval 0.27-3.15, p = 0.91). Survival analysis showed that amongst the dichorionic twins the hazard of death continued to rise throughout gestation. In contrast, the hazard of death for the monochorionic twins rose gradually to a maximum at 28 weeks' gestation and was then constant. CONCLUSION: Chorionicity did not affect the overall fetal loss rate amongst the twin pregnancies in our setting. There were differences in patterns of loss according to chorionicity, which require further investigation.     

Perinatal outcomes of twin pregnancies discordant for major fetal anomalies

OBJECTIVE: The aim of this study was to determine perinatal outcomes of twin pregnancies discordant for a major fetal anomaly and to compare with twins without anomaly. METHODS: All twin pregnancies admitted or referred to the maternal-fetal unit were prospectively entered into a computer database. Chorionicity, fetal anomaly, mean gestational age at delivery, birth weight and perinatal survival rate were reviewed. MAIN OUTCOME MEASURES: Mean gestational age at delivery, birth weight and perinatal survival rate of twins with and without anomaly. RESULTS: There were 48 cases of monochorionic diamniotic (MCDA), 2 cases of monochorionic monoamniotic (MCMA) and 217 twins with dichorionic (DC) placentation. Out of 267 twin pregnancies, there were 17 (6.3%) twins with fetal anomaly. Twins discordant for a major fetal anomaly were diagnosed in 13 cases (4.8%). We observed 3 cases with MCDA and 10 cases with DC placentation and the incidence of discordance for a major fetal anomaly as 4.6% (10/217) in DC and 6.0% (3/50) in MC twin pregnancies. We identified 8 cases (62%) with craniospinal, 2 (15%) with gastrointestinal, 2 (15%) with urinary system, and 1 case (8%) with both craniospinal and gastrointestinal anomalies. There were significant differences between the normal co-twin of the major anomaly group (n = 13) and twins without anomaly group (n = 235) in mean gestational age at delivery (32 vs. 34 weeks; p = 0.029), mean birth weight (1,640 vs. 2,030 g; p = 0.022) and perinatal survival rate (69.2 vs. 91.1%; p = 0.018), respectively. CONCLUSION: The presence of a fetus with a major anomaly in a twin gestation increases the risk of preterm delivery, low birth weight and perinatal mortality of the normal co-twin.     

Perinatal outcome and neurological follow up of the cotwins in twin pregnancies complicated by single intrauterine death

Objective

To review the outcome of twin pregnancies complicated by single fetal intrauterine death (IUD) managed at our Centre and to evaluate the neurological follow up of the surviving cotwins.

Study design

Twenty-three twin pregnancies (10 dichorionic and 13 monochorionic diamniotic) complicated by IUD in the II or III trimester were seen at our Centre during the study period (2001–2006). All patients were managed conservatively unless non-reassuring signs of fetal well-being were present at ultrasound examination or CTG after 28 weeks, suggesting immediate delivery. Serial scans after the diagnosis of single death were performed and, in addition, eight monochorionic twin pregnancies underwent prenatal MRI in order to identify the presence of cerebral lesions in the survivors. Live born surviving cotwins underwent neurological follow up.

Results

In the monochorionic group one cotwin died in utero and one in the neonatal period with a perinatal survival rate of 83.4% (10/12) (excluding one case who opted for termination of pregnancy); in the dichorionic group perinatal survival rate was 100%. In all monochorionic cases there were no signs of ischemic brain lesions in the surviving cotwins at the diagnosis of single death and during ultrasonographic follow up. In monochorionic pregnancies prenatal MRI, when performed, was negative for signs of brain damage in the surviving cotwins. Gestational age at delivery was not statistically different between monochorionic and dichorionic pregnancies (36 (range, 28.4–40.2) vs. 34.6 (range, 28.2–41.3) weeks) (p = 0.6) and the rate of early preterm delivery before 32 weeks was 23.8% (5/21) and independent from chorionicity (18.2% vs. 30%, p = 0.5). Neurodevelopmental follow up was available for 18/20 live born survivors (85%) and was normal in all but one twin; this case was born from a dichorionic pregnancy with a suspicion of congenital infection.

Conclusions

Our data confirmed a trend to a higher risk of perinatal mortality of cotwins in monochorionic twin pregnancies compared to dichorionic ones. In our experience prenatal ultrasound and MRI were useful to exclude cerebral lesions in utero and subsequent neurological sequelae in surviving monochorionic cotwins, even if definitive conclusions, especially on MRI, are limited by the small number of cases in our study.     

Clinical evaluation of the risk of twin-to-twin transfusion syndrome using the relative power contribution of fetal heart rate fluctuations

OBJECTIVES: In twin pregnancies, it has been suggested that fluctuations of the two fetal heart rates should be considered as two variates that affect each other. We therefore investigated whether the relative power contribution (RPC) of heart rate fluctuation between twins reflects the clinical severity of twin-to-twin transfusion syndrome. STUDY DESIGN: Sixty-three cases of twin pregnancy including 43 monochorionic twins and 20 dichorionic twins were studied. Thirteen monochorionic twins with polyhydramnios in one twin were regarded as twin-to-twin transfusion syndrome (TTTS). Of the 13 TTTS cases, 8 cases with polyhydramnios in one twin and oligohydramnios in the other were deemed to be a 'stuck' twin. The RPC of the very low frequency domain (VL; 0.0125-0.0625 Hz) of fetal heart rate fluctuation in the twin fetuses of monochorionic and dichorionic pregnancies was obtained within a week of delivery. The relationship between the value of the RPC and the outcome of these twins was examined. RESULTS: For both monochorionic and dichorionic twins the RPC of twin fetuses was significantly higher in TTTS twins than in twins without TTTS. In particular, in pregnancies that resulted in fetal death, early neonatal death, or hydrops of one of the twins, this twin had a higher RPC than the other twin. No significant difference was observed in the RPC value between twins of either monochorionic or dichorionic pregnancies that did not develop TTTS. Serial changes in RPC values were followed in 7 cases of TTTS. The RPC value rose rapidly just before delivery in three cases with resultant poor outcome. CONCLUSION: A rapid change in the RPC of twin fetuses measured using the VL frequency domain of fetal heart rate fluctuations may predict poor outcome in twin pregnancies.     

Should apparently uncomplicated monochorionic twins be delivered electively at 32 weeks?

Objectives.?We aimed to estimate the optimal time of delivery and investigated the residual risk of fetal death after viability in otherwise uncomplicated monochorionic diamniotic twin pregnancies.

Study design.?A database of 576 completed multiple pregnancies that were managed in our tertiary referral fetal medicine department between 1996 and 2007 was reviewed and the uncomplicated 111 monochorionic and the 290 dichorionic diamniotic twin pregnancies delivered after 24 weeks were selected. The rate of fetal death was derived for two-week periods starting at 24 weeks’ gestation and the prospective risk of fetal death was calculated by determining the number of intrauterine fetal deaths that occurred within the two-week block divided by the number of continuing uncomplicated monochorionic twin pregnancies during that same time period.

Results.?The unexpected single intrauterine deaths rate was 2.7% versus 2.8% in previously uncomplicated monochorionic and dichorionic diamniotic pregnancies, respectively. The prospective risk of unexpected stillbirth after 32 weeks of gestation was 1.3% for monochorionic and 0.8% for dichorionic pregnancies.

Conclusions.?In otherwise apparently uncomplicated monochorionic diamniotic pregnancies this prospective risk of fetal death after 32 weeks of gestation is lower than reported and similar to that of dichorionic pregnancies, so does not sustain the theory of elective preterm delivery.     

Fetoscopic surgery in triplet pregnancies: a multicenter case series

OBJECTIVE: The purpose of this study was to evaluate the feasibility of fetoscopic surgery in complicated monochorionic and dichorionic triplet pregnancies. STUDY DESIGN: This was a case series of fetoscopic surgery in 12 cases of monochorionic (n = 5) or dichorionic (n = 7) triamniotic triplets complicated by severe feto-fetal transfusion (n = 8), twin reversed arterial perfusion sequence (n = 3), or discordant for an anomaly (n = 1). Six underwent cord occlusion, and 6 had laser coagulation of the vascular anastomoses. RESULTS: All procedures were successfully completed, and the outcome was comparable to that reported for similar procedures in twins. Eighty-three percent of fetuses survived, and 13% had long-term problems. CONCLUSION: Fetoscopic surgery may be considered as a therapeutic option in complicated triplet pregnancies, with results similar to those found in twins.     

Screening for trisomy 21 in twin pregnancies in the first trimester: an update of the impact of chorionicity on maternal serum markers

OBJECTIVE: To examine the distribution of first-trimester biochemical markers of aneuploidy in twin pregnancies, and to assess whether there are differences in the distributions between monochorionic and dichorionic twins. METHODS: Maternal serum-free beta-hCG and PAPP-A were measured between 11 + 0 and 13 + 6 weeks as part of a routine first-trimester screening program in conjunction with fetal nuchal translucency (NT) performed at two sites. Data from twin pregnancies were extracted from the fetal databases along with information on the chorionicty. The individual marker concentrations were expressed as weight corrected, ethnicity corrected, smoking corrected and IVF corrected MoM using data from singleton pregnancies as the reference. The overall medians were compared to those in singleton pregnancies and between monochorionic and dichorionic twins. RESULTS: Data was available from 1914 sets of twins. Of these, 1214 had information with respect to chorionicity, with 1024 being dichorionic and 190 being monochorionic. The overall median weight corrected, ethnicity corrected, smoking corrected and IVF corrected MoM amongst twin pregnancies were 2.023 for free beta-hCG (sd log(10) MoM = 0.2611 and 2.121 for PAPP-A (sd log(10) MoM = 0.2255) -- both medians were significantly greater than the medians in singleton pregnancies (1.00 MoM). In the case of monochorionic and dichorionic twins the median weight corrected, ethnicity corrected, smoking corrected and IVF corrected, free beta-hCG MoM's were not significantly different (1.983 v 2.041), however for PAPP-A the median weight corrected, ethnicity corrected, smoking corrected and IVF corrected MoM in monochorionic twins was significantly lower than in dichorionic twins (1.756 v 2.250) whilst the sd log(10) MoM's were not significantly different (0.2185 v 0.2167). CONCLUSION: Screening in twin pregnancies requires adjustment of the calculated MoM to account for the presence of two fetuses. In general, for free beta-hCG, this should be by dividing the observed corrected MoM by 2.023. For PAPP-A two different factors are required - 2.192 in dichorionic twins and 1.788 in monochorionic twins.     

Single intrauterine death in twin pregnancy: Evidenced-based counselling and management

Twins have a significantly higher risk of stillbirth, preterm delivery, perinatal morbidity and mortality. Single intrauterine fetal death is a relatively common and devastating occurrence for families and clinicians alike. Monochorionic twins are up to 13 times more likely to suffer an intrauterine death when compared to singletons. Additionally, longer term neurological sequelae affect monochorionic twins disproportionately. The timing of the death of the co-twin and the fetal order at the time of death have an impact on the outcome for the survivor. The risk in dichorionic pregnancies is lower with respect to neurological injury; however, the risk of prematurity remains high, particularly where the leading twin dies in utero. Recent published studies report lower rates of neurological injury in monochorionic twin pregnancies that incur an intrauterine fetal death after foetoscopic laser ablation for twin-to-twin transfusion syndrome – an important finding for patient counselling.Tweetable abstractSingle intrauterine fetal death in twins is a relatively common and devastating occurrence for families and clinicians alike. Adhering to collegiate guidelines will likely reduce but not eliminate the incidence of SIUD in twins.     

Umbilical cord complications in twin pregnancies

OBJECTIVES: The postpartum umbilical cord examination can provide a lot of significant information concerning discordant twin growth or reasons of intrauterine death of one or all the fetuses. The aim of this study was the postpartum assessment of umbilical cords in twin pregnancies. MATERIAL AND METHODS: The examination material consisted placentas coming from 110 twin pregnancies. The analysis concerned the assessment of placenta types, the umbilical cords attachment place and also the twins birth weight. RESULTS: Basing on the studies of placentas coming from 110 twin pregnancies 76 (69.0%) dichorionic and 34 (31.0%) monochorionic placentas were found. Among dichorionic, 40 (53%) separated and 36 (47%) fused placentas were observed. Among monochorionic 31 (91%) diamniotic and 3 (9.0%) monoamniotic placentas were present. Abnormal umbilical insertion to placenta was most frequently observed in monochorionic pregnancies: in diamniotic--marginal insertion in 21.2%, velamentous insertion in 15.9%, and in monoamniotic--equally 33.3%. In dichorionic pregnancies, for fused placentas--marginal in 8.7%, velamentous in 9.1%, and for separated--5.6% and 3.1%. CONCLUSIONS: The abnormal umbilical cord insertions to the placenta was most frequently found in monochorionic pregnancies. Among pairs of twin born with body weight discordance, the abnormal umbilical cord insertion was more frequently found in the case of the smaller newborn.     

Screening for trisomy 21 in twin pregnancies in the first trimester: does chorionicity impact on maternal serum free beta-hCG or PAPP-A levels?

In a study of 180 twin pregnancies I have examined the distribution of maternal serum free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A), in addition to fetal nuchal translucency thickness (NT), in twins classified as monochorionic or dichorionic, based on ultrasound appearance at 10-14 weeks of gestation. In 45 monochorionic and 135 dichorionic twin pregnancies the median MoM free beta-hCG was not significantly different (1.00 vs 1.01), whilst that for PAPP-A was lower (0.89 vs 1.01) but again with no statistical significance. Previous reports of an increased fetal NT in monochorionic twins pregnancies could not be confirmed (1.03 vs 1.00). It is concluded that the existing pseudo risk twin correction algorithm is appropriate for both monochorionic and dichorionic twins in providing accurate first trimester risks for trisomy 21.     

Mode of delivery and neonatal outcome in uncomplicated monochorionic twin pregnancies

Objective: The association between of mode of delivery and perinatal morbidity in monochorionic (MC) twins is not clear. Thus there is no agreement regarding the optimal mode of delivery of MC twins. The aim of this study is to determine the impact of the mode of delivery on neonatal outcome of uncomplicated MC twins in a tertiary center with a strict policy of delivering MC twins by 37 weeks’ gestation. Methods: Retrospective analysis of all uncomplicated MC twin deliveries at a tertiary referral hospital during a 5-year period. Complicated MC pregnancies (fetal death, selective reduction, twin to twin transfusion syndrome, fetal growth restriction of one or both twins or major fetal anomalies) were excluded. Induction of labor or planned caesarean sections of uncomplicated MC pregnancies was conducted between 35 and 37 weeks of gestation. Neonatal outcomes of MC twins were compared according to the mode of delivery. Moreover, mode of delivery was compared with a control group of 1934 dichorionic (DC) twin pregnancies delivered during the same period. Results: The rate of Caesarean section was 63.4% in uncomplicated MC/DA twins pregnancies and this was similar to our rate in DC twins (61%, p = 0.65). Multivariate analysis revealed that adverse neonatal outcome was significantly associated with gestational age at delivery, neonatal birth weight discordance and male gender but not with the intended or actual mode of delivery. Conclusion: Delivering MC twin pregnancies by 37 weeks’ gestation is associated with similar rate of vaginal deliveries compared with DC twin pregnancies. The neonatal outcome was not affected by the mode of delivery, and therefore vaginal delivery seems safe in MC twins.     

Intertwin crown-rump length discordance in the prediction of fetal anomalies,fetal loss and adverse perinatal outcome

Objective: To assess the risks of fetal anomalies, fetal loss and adverse perinatal outcome in a cohort of first-trimester intertwin crown-rump length (CRL) discordant twins, stratified by chorionicity and the degree of CRL discordance.

Method: Four-hundred-and-seventy-one twin pregnancies were scanned during an 8-year period at 11–14 weeks, and those with an intertwin CRL discordance ≥10% were compared with concordant twins. Outcomes were also compared between monochorionic and dichorionic twins and between moderate (10–16%) and severe (>16%) discordance.

Results: Four-hundred-and-five twin pregnancies, 65 discordant and 340 concordant, were follow-up. Discordant twin pregnancies were at significant higher risk of chromosomal (OR?=?11.42; 95%?CI: 2.78–46.94) and structural anomalies (OR?=?5.91; 95%?CI: 2.25–15.54), spontaneous fetal loss (OR?=?4.23; 95%?CI: 1.79–10.01), birthweight discordance (OR?=?2.8; 95%?CI: 1.48–5.65) and small-for-gestational age (OR?=?3.48; 95% CI: 1.78–6.79). Similar differences (except for birthweight discordance) were observed among dichorionic twins. Among monochorionic, increased frequencies were only seen for structural anomalies, birthweight discordance and small newborns. Severe CRL discordance presented with higher rates of structural anomalies, stillbirth, birthweight discordance and small newborns.

Conclusion: Intertwin CRL discordance (≥10%) results in an increased risk of fetal anomalies and growth restriction that increases in severe CRL discordance (≥16%).     

Detecting fetal growth restriction or discordant growth in twin gestations stratified by placental chorionicity

OBJECTIVE: To use recommendations made by the Evidence-Based Medicine Working Group to determine the accuracy of sonographically estimated fetal weight to diagnose fetal growth restriction (FGR) (estimated or actual birth weight < 10% for gestational age [GA]) or discordancy in dichorionic and monochiorionic twin gestations. STUDY DESIGN: The inclusion criteria for this retrospective analysis were nonanomalous twins, reliable GA and sonographic estimate of fetal weight within 21 days of live births of both fetuses beyond 26 weeks. For likelihood ratio (LR) and odds ratio (OR), 95% confidence intervals (CIs) were calculated. RESULTS: Over 52 months, 126 twin gestations met the inclusion criteria; 29% were monochorionic and 71% dichorionic. The incidence of FGR in 1 of monochorionic twin fetuses (46%) was twice as high as in dichorionic (26%; OR 2.01; 95% CI 1.00, 4.03), but the rates of discordance > or = 20% were similar (21% vs. 18%, respectively; OR 1.26; 95% CI 0.64, 2.47). The LR (95% CI) of detecting discordant growth > or = 20% was 6.1 (2.5, 15.1) for dichorionic twins and 6.0 (1.8, 20.0) for monochorionic. The LR of identifying FGR in twin A and B in dichorionic twins was 6.3 (2.0, 19.7) and 8.7 (2.9, 26.9), respectively; the corresponding LR for monochorionic twins was 14.5 (1.9, 112.3) and 18.7 (2.6, 135.1). To determine the number of twins required for a tight confidence interval around an LR of 10, post hoc sample size calculations indicated: (1) regardless of chorionicity, attaining LR > 10 is not feasible; (2) in dichorionic twins, detection of FGR with twin A or B is not possible; and (3) about 500 monochorionic pregnancies are necessary to ensure that estimated fetal weight can accurately identify FGR. CONCLUSION: Using guidelines proposed by the Evidence-Based Medicine Working Group, at present it may not befeasible to identify aberrant growth in twins.