摘要：Objective: The purpose of this study was to identify the gestational age with the lowest morbidity and mortality rates for twin pregnancies that reach term. Study design: 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 ≥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. Results: 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 ≥40 weeks of gestation group for twin A and B(Apgar score, ≤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 ≥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). Conclusion: 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.