Perinatal mortality and neonatal morbidity rates among twin pairs at different gestational ages: Optimal delivery timing at 37 to 38 weeks’ gestation

Objective: The aim of this study was to determine the gestational age at delivery associated with the lowest rates of perinatal mortality, respiratory distress syndrome, and long hospital stays among twins, with pair rates used to account for both infants in each twin pregnancy. Study Design: We conducted a population-based retrospective study that analyzed linked birth certificates, fetal and infant death certificates, and hospital discharge data for 8150 twin pairs born in Washington State during 1987 through 1997. The χ2 or Fisher exact test was used to assess the statistical significance. Results: The nadirs of perinatal mortality rate, respiratory distress syndrome incidence, and long hospital stay rate were seen at delivery dates of 39, 40, and 38 weeks’ gestation, respectively. Restriction to pairs delivered vaginally without the induction of labor revealed that the perinatal mortality rate was lowest for delivery at 37 weeks’ gestation, the gestational age at which the highest numbers of such spontaneously timed pairs were born. Conclusion: Induction of labor should be routinely considered for twins at 37 to 38 weeks’ gestation. (Am J Obstet Gynecol 2001;184:451-8.)