Fetal reduction of triplet pregnancies to twins vs singletons: a meta-analysis of survival and pregnancy outcome

Objective: This systematic review and meta-analysis aimed to compare the fetal survival rate and perinatal outcomes of triplet pregnancies after selective reduction to twin pregnancies vs singleton pregnancies. Data Sources: PubMed, Web of Science, Scopus, and Embase were systematically searched from the inception of the databases to January 16, 2022. Study Eligibility Criteria: Studies comparing the survival and perinatal outcomes between reduction to twin pregnancies and reduction to singleton pregnancies were included. The primary outcomes were fetal survival, defined as a live birth at >24 weeks of gestation. The secondary outcomes were gestational age at birth, preterm birth at <32 and <34 weeks of gestation, early pregnancy loss (<24 weeks of gestation), low birthweight, and rate of neonatal demise (up to 28 days after birth). Methods: The random-effect model was used to pool the mean differences or odds ratios and the corresponding 95% confidence intervals. To provide a range of expected effects if a new study was conducted, 95% prediction intervals were calculated for outcomes presented in >3 studies. Results: Of note, 10 studies with 2543 triplet pregnancies undergoing fetal reduction, of which 2035 reduced to twin pregnancies and 508 reduced to singleton pregnancies, met the inclusion criteria. Reduction to twin pregnancies had a lower rate of fetal survival (odds ratio, 0.61; 95% confidence interval, 0.40–0.92; P=.02; 95% prediction interval, 0.36–1.03) and comparable rates of early pregnancy loss (odds ratio, 0.89; 95% confidence interval, 0.58–1.38; P=.61; 95% prediction interval, 0.54–1.48) and neonatal demise (odds ratio, 0.57; 95% confidence interval, 0.09–3.50; P=.55) than reduction to singleton pregnancies. Reduction to twin pregnancies had a significantly lower gestation age at birth (weeks) (mean difference, −2.20; 95% confidence interval, −2.80 to −1.61; P<.001; 95% prediction interval, −4.27 to −0.14) than reduction to singleton pregnancies. Furthermore, reduction to twin pregnancies was associated with lower birthweight and greater risk of preterm birth at <32 and <34 weeks of gestation. Conclusion: Triplet pregnancies reduced to twin pregnancies had a lower fetal survival rate of all remaining fetuses, lower gestational age at birth, higher risk of preterm birth, and lower birthweight than triplet pregnancies reduced to singleton pregnancies; reduction to twin pregnancies vs reduction to singleton pregnancies showed no substantial difference for the rates of early pregnancy loss and neonatal death.