Elective birth at 37 weeks of gestation versus standard care for women with an uncomplicated twin pregnancy at term: the Twins Timing of Birth Randomised Trial

Abstract

The majority of women with a twin pregnancy give birth preterm, but about 46% deliver after 37 weeks of gestation. Several population-based studies have reported that there is a higher risk of perinatal mortality and morbidity among women with a twin pregnancy continuing beyond 37 weeks of gestation with advancing gestational age. The Twins Timing of Birth Randomised Trial was a multicenter controlled study designed to determine whether elective timing of birth at 37 weeks of gestation among women with an uncomplicated twin pregnancy was associated with reduced risk of death or serious outcomes for babies, without increased harms in either the woman or the infants. All participants were at 36 6/7 weeks of gestation, dichorionic or monochorionic, with no contraindication to continuing their pregnancy. Eligible women were randomized to either an elective birth group (birth at 37 weeks, n = 116) or a standard care group (expectant management with birth planned from 38 weeks, n = 119). Outcome assessors were blinded to treatment allocation. The primary study outcome measure was a composite of serious adverse outcome for the infant. Among women with an uncomplicated twin pregnancy, there was a significantly reduced risk of serious adverse outcome for infants with elective birth at 37 weeks of gestation (elective birth: 4.7% [11/232] vs standard care: 12.2% [29/238]; the risk ratio [RR] was 0.39, with a 95% confidence interval [CI] of 0.20–0.75; P = 0.005). The only individual outcome that differed between the 2 groups was a reduced risk of birth weight less than the third centile for gestational age and infant sex (elective birth group: 3.0% [7/232] vs standard care group: 10.1% [24/238]; RR, 0.30; 95% CI, 0.13–0.67; P = 0.004). However, when they conducted a post hoc analysis using twin gestational age–specific growth charts, there was still a small difference in the primary composite of serious adverse infant outcome (elective birth group: 1.7% [4/232] vs standard care group: 5.0% [12/238]; the RR was 0.34, with a 95% CI of 0.11–1.05; P = 0.06), but it was no longer statistically significant.