Prospective Risk of Stillbirth and Neonatal Complications in Twin Pregnancies: Systematic Review and Meta-analysis

Twin pregnancies are at increased risk of stillbirth. Uncomplicated twin pregnancies are commonly delivered earlier to prevent stillbirth; however, there is a risk of neonatal complications associated with being born prior to 39 weeks’ gestation. The optimal gestational age for delivery in twin pregnancies is unknown and likely varies by chorionicity. The present study aimed to determine the prospective risk of stillbirth in women with uncomplicated monochorionic and dichorionic twin pregnancies, and neonatal mortality risks, when delivered beyond 34 weeks of gestation. Data on twin pregnancies that reported rates of stillbirth were obtained from MEDLINE, EMBASE, and Cochrane Library. Separate analyses for risks of stillbirth and neonatal death in monochorionic and dichorionic twin pregnancies were undertaken from 34 weeks’ gestation and further and early preterm (<34 weeks’) gestation. The risk of neonatal outcomes was estimated every week by multilevel random-effects logistic regression models, and point estimates of the risk of each event were obtained by the gestational period with its corresponding 95% confidence interval (CI). Results for the dichorionic twin pregnancies indicated that the prospective risk of stillbirth was 1.2 per 1000 pregnancies (95% CI, 0.7–1.8) at 34 weeks, with the related risk of neonatal death of 6.7 per 1000 pregnancies (95% CI, 3.3–13.5). The stillbirth risk was found to be significantly lower than the risk of neonatal death at 34 weeks (risk difference, -5.8/1000) and 35 weeks (-5.1/1000). The perinatal risks were balanced at 37 + 0–6 weeks (1.2/1000, -1.3 to 3.6/1000), beyond which the risks of stillbirth (10.6/1000) outweighed the risk of neonatal death significantly (1.5/1000) from delivery at the same gestational age (risk difference, 8.8/1000, 3.6–14). The prospective risk of stillbirth and neonatal mortality rates in monochorionic pregnancies at 34 weeks’ gestation were 0.9/1000 (95% CI, 0.1–3.4) and 12.1/1000 (95% CI, 4.2–34.3), respectively. The risks of neonatal death were greater than the risks of stillbirth at 34 weeks (risk difference, -15.6/1000) and 35 weeks (risk difference, -2.4/1000). A trend in which the risk of stillbirth (9.6/1000; 95% CI, 3.9–19.7) was higher than the risk of neonatal death (3.6/1000; 95% CI, 1.2–11.1) with a risk difference of 2.5/1000 (95% CI, -12.4 to 17.4/1000; I2 = 0%) was observed after 36 + 0–6 weeks. The study concluded that delivery should be considered at 37 weeks of gestation in uncomplicated dichorionic twin pregnancies and at 36 weeks of gestation in monochorionic pregnancies to reduce the incidence of perinatal deaths.