Objective To evaluate mortality and morbidity in a large cohort of twin pregnancies according to chorionicity. We aimed to estimate the optimal time of delivery.Design Historical cohort design.Setting Two teaching hospitals.Population Twin pregnancies delivered in the University Medical Centre, Utrecht, and the St Elisabeth Hospital, Tilburg (1995Tilburg ( -2004, The Netherlands (n = 1407).Methods Pregnancy outcomes were documented according to chorionicity. Mortality ‡32 weeks was reviewed carefully with special attention to antenatal fetal monitoring, autopsy and placental histopathology to find an explanation for adverse outcome.Main outcome measures Perinatal mortality and morbidity in monochorionic (MC) and dichorionic (DC) twins.Results Perinatal mortality was 11.6% in MC twin pregnancies and 5.0% in DC twin pregnancies. After 32 weeks, the risk of intrauterine death (IUD) was significantly higher in MC twins than in DC twins (hazard ratio 8.8, 95% CI 2.7-28.9). In most of these cases of IUD, no antenatal signs of impaired fetal condition had been present. Median gestational age was 1 week longer in DC twins than in MC twins, and the mean birthweight was 221 g higher. Severe birthweight discordancy (>20%) occurred more often in MC twins than in DC twins (OR 1.23, 95% CI 0.97-1.55). The incidence of necrotising enterocolitis (NEC) was higher in MC twins, after adjustment for age and weight at birth (OR 4.05, 95% CI 1. 97-8.35). There was a trend towards higher neuromorbidity in MC twins.Conclusions This is the largest cohort study of twin pregnancies evaluating outcome according to chorionicity thus far. MC twins are at increased risk for fetal death (even at term), NEC and neuromorbidity. Current antenatal care is insufficient to predict and prevent this excess perinatal mortality and morbidity. Planned delivery at or even before 37 weeks of gestation seems to be justified for MC twins.

Objective To determine the risks of stillbirth and neonatal complications by gestational age in uncomplicated monochorionic and dichorionic twin pregnancies.Design Systematic review and meta-analysis.Data sources Medline, Embase, and Cochrane databases (until December 2015). Review methods Databases were searched without language restrictions for studies of women with uncomplicated twin pregnancies that reported rates of stillbirth and neonatal outcomes at various gestational ages. Pregnancies with unclear chorionicity, monoamnionicity, and twin to twin transfusion syndrome were excluded. Meta-analyses of observational studies and cohorts nested within randomised studies were undertaken. Prospective risk of stillbirth was computed for each study at a given week of gestation and compared with the risk of neonatal death among deliveries in the same week. Gestational age specific differences in risk were estimated for stillbirths and neonatal deaths in monochorionic and dichorionic twin pregnancies after 34 weeks’ gestation.Results 32 studies (29 685 dichorionic, 5486 monochorionic pregnancies) were included. In dichorionic twin pregnancies beyond 34 weeks (15 studies, 17 830 pregnancies), the prospective weekly risk of stillbirths from expectant management and the risk of neonatal death from delivery were balanced at 37 weeks’ gestation (risk difference 1.2/1000, 95% confidence interval −1.3 to 3.6; I2=0%). Delay in delivery by a week (to 38 weeks) led to an additional 8.8 perinatal deaths per 1000 pregnancies (95% confidence interval 3.6 to 14.0/1000; I2=0%) compared with the previous week. In monochorionic pregnancies beyond 34 weeks (13 studies, 2149 pregnancies), there was a trend towards an increase in stillbirths compared with neonatal deaths after 36 weeks, with an additional 2.5 per 1000 perinatal deaths, which was not significant (−12.4 to 17.4/1000; I2=0%). The rates of neonatal morbidity showed a consistent reduction with increasing gestational age in monochorionic and dichorionic pregnancies, and admission to the neonatal intensive care unit was the commonest neonatal complication. The actual risk of stillbirth near term might be higher than reported estimates because of the policy of planned delivery in twin pregnancies.Conclusions To minimise perinatal deaths, in uncomplicated dichorionic twin pregnancies delivery should be considered at 37 weeks’ gestation; in monochorionic pregnancies delivery should be considered at 36 weeks.Systematic review registration PROSPERO CRD42014007538.

Objective: The purpose of this study was to determine the perinatal outcome in monoamniotic twin pregnancies and to review the recently published literature about the topic. Methods: This retrospective study examined the records of prenatally diagnosed monoamniotic twin pregnancy casese in our institution between January 1997 and April 2010. Results: Among 1,112 twin pregnancies, there were 15 (1.3%) monoamnionic twins, including 2 conjoined twin pregnancies. Twelve (80%), 9 (60%), 5 (33.3%), and 4 pregnancies (26.7%) delivered after 20, 30, 32, and 34 weeks, respectively. Among 12 pregnancies that continued after 20 weeks of gestation, three cases showed one-fetal death and one, both-fetal death. The perinatal mortality rate (from 20 weeks of gestation to 28 days after birth) was 37.5%. The incidence of lethal anomalies and congenital heart anomalies was 20% and 23.3%, respectively. The mean gestational age at delivery was 31.4±4.53 weeks; 16 of 18 neonates (84.2%) were admitted to the neonatal intensive care unit (NICU). Three neonates expired on the first day after birth. The mean duration of the NICU stays for 13 live neonates was 32.0±29.3 days (range, 3 to 114 days). The main causes of perinatal deaths were preterm birth, congenital anomalies, pregnancy loss before 20 weeks, and intrauterine fetal demise that might have resulted form cord entanglement. Conclusion: Perinatal mortality in monoamniotic twins was still very high and the survival rate after 32 weeks of gestation is approximately one-third. Further studies are needed to improve the perinatal mortality.