Neonatal mortality and morbidity rates in term twins with advancing gestational age

The purpose of this study was to identify the gestational age with the lowest morbidity and mortality rates for twin pregnancies that reach term.

A retrospective cohort study carried out with 60,443 twin pairs from the United States (1995-1997). Analysis was restricted to pregnancies that had reached at least 37 weeks of gestation; groups were created on the basis of the gestational ages of 37, 38, 39, and > or = 40 weeks. The incidence of death and morbidity were calculated; multiple logistic regression models were used to estimate the independent effect of gestational age for twin A and B.

The neonatal mortality rate increased significantly after 40 weeks of gestation (twin A: odds ratio, 3.47 [95% CI, 2.29, 5.38]; twin B, odds ratio, 2.52 [95% CI, 1.75, 3.67]). There was also an increased risk of neonatal morbidity in the > or = 40 weeks of gestation group for twin A and B (Apgar score, < or = 3; odds ratio, 1.88 [95% CI, 1.18, 3.02], 1.74 [95% CI, 1.21, 2.52], respectively). There was a decreased risk of assisted ventilation in the 38 and 39 weeks of gestation group for twin A (odds ratio, 0.86 [95% CI, 0.77, 0.97], odds ratio, 0.83 [95% CI, 0.72, 0.95], respectively) and a decreased risk in the 39 and > or = 40 weeks of gestation groups for twin B (assisted ventilation: odds ratio, 0.83 [95% CI, 0.73, 0.93], odds ratio, 0.81 [95% CI, 0.72, 0.92], respectively).

This study suggests that the optimal date of delivery for twins should be <40 weeks of gestation; there was no compelling evidence for delivering at <38 weeks of gestation.