Twin Delivery Should Be at 37 Weeks to Minimize Deaths

Veronica Hackethal, MD

September 07, 2016

In uncomplicated dichorionic twin pregnancies, delivery should be considered at 37 weeks' gestation to minimize perinatal death, and no clear evidence supports delivery of monochorionic twins before 36 weeks, according to a meta-analysis published online September 6 in the BMJ.

"Our study provides comprehensive estimates comparing risks of stillbirth and neonatal mortality at various gestational ages, which is required for the planning of delivery in uncomplicated twin pregnancies," write Fiona Cheong-See, MBBS, from Queen Mary University of London, United Kingdom, and colleagues with the Global Obstetrics Network Collaboration.

The study is the largest to date to evaluate stillbirths and neonatal outcomes in twin pregnancies, and the first to estimate neonatal morbidity for specific gestational ages.

Twin pregnancies carry a higher risk for stillbirth than singleton pregnancies, and the risk increases with gestational age. Although uncomplicated twin pregnancies are often scheduled for early delivery to prevent stillbirth, preterm birth can increase neonatal complications.

Yet, the optimal age for delivery of twin pregnancies has not been established. Current recommendations vary from 34 to 37 weeks' gestation in monochorionic pregnancies that share a placenta, and 37 to 39 weeks in dichorionic pregnancies that have two placentas, according to background information in the article.

In the study, researchers did a systematic review of studies published in any language through December 2015. Then they performed a meta-analysis to evaluate the risk for stillbirth and neonatal complications in weekly intervals for monochorionic and dichorionic twin pregnancies, starting from 34 weeks' gestation. They also analyzed studies for risk for bias and representativeness and defined neonatal mortality as death up to 28 days after delivery.

The analysis included 32 studies covering 35,171 twin pregnancies (29,685 dichorionic, 5486 monochorionic).

In dichorionic twins delivered at 37 weeks, the weekly risk for stillbirth with watchful waiting balanced the risk for neonatal death from delivery (pooled risk difference, 1.2/1000 pregnancies; 95% confidence interval, −1.3 to 3.6; I 2 = 0%).

After 37 weeks' gestation, the risk for still birth significantly outweighed the risk for neonatal death from delivery. Delaying delivery by just 1 week (to 38 weeks) resulted in an additional 8.8 perinatal deaths per 1000 pregnancies (95% confidence interval, 3.6 - 14.0 deaths per 1000 pregnancies; I 2 = 0%).

Monochorionic pregnancies delivered at 34 and 35 weeks had a higher risk for neonatal death than stillbirth, but the results were not significant. After 36 weeks, results showed a nonsignificant trend toward higher risk for stillbirth compared with neonatal death (pooled risk difference, 2.5; 95% confidence interval, −12.4 to 17.4/1000; I 2 = 0%).

Rates of neonatal morbidity, including assisted ventilation, respiratory distress syndrome, admission to the neonatal intensive care unit, and septicemia, consistently decreased as gestational age increased in both monochorionic and dichorionic gestations.

The authors point out that current policies for planned elective delivery of twins before term could have decreased the number of twins born at term, which may have underestimated the risk for stillbirth near term.

"Our estimates of fetal and neonatal outcomes at various gestational ages in twin pregnancies should be taken into account when decisions are made on timing of delivery," the authors conclude. "The information on risks provided in twin pregnancies will complement the ongoing national and international efforts to reduce the rates of stillbirths and unexpected neonatal complications in babies born near term."

"We welcome this robust systematic review which provides us with a comprehensive picture on stillbirths and neonatal outcomes in twin pregnancies," said Mark Kilby, MD, professor of Fetal Medicine and spokesperson for the Royal College of Obstetricians and Gynaecologists, in a related press release.

"The study confirms existing findings of previous studies and adds further objectivity to the NICE guidelines on the management of twin pregnancies. Timing of delivery for multiple pregnancies should be always be individualised, however, the current evidence-base suggests that in uncomplicated dichorionic twin pregnancies delivery should be considered at 37 weeks' gestation and in monochorionic pregnancies delivery should be considered from 36 weeks," he continued.

The authors have disclosed no relevant financial relationships.

BMJ. 2016;354:i4353. Full text

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