GESTATIONAL DURATION IN THE PREGNANCY AFTER A PRETERM TWIN DELIVERY

OBJECTIVE: This was a population-based medical birth registry investig ation designed to study whether a preterm twin delivery portends a sho rter gestation in a subsequent pregnancy. STUDY DESIGN: Data on all pr egnancies and deliveries from 1973 to 1993 inclusive, stored at the Me dical Birth Registry, the National Board of Health acid Welfare, Stock holm, were analyzed. Information on gestational duration, estimated du ring pregnancy with or without ultrasonography in the second trimester , was analyzed for 2979 twin births followed by a singleton delivery. RESULTS: Gestation for women with a singleton pregnancy after a preter m twin birth in the twenty-eighth to thirty-sixth gestational week las ted about 39 +/- 0.5 weeks (mean +/- SEM). When the twin birth had tak en place at term (37 to 42 weeks) the corresponding singleton gestatio n lasted about a week longer. When the twin birth occurred in gestatio nal weeks 28 to 30, 31 to 33, or 34 to 36, the corresponding proportio ns of women who gave birth earlier than 37 weeks (20 to 27 weeks, only live births) in the subsequent singleton pregnancy were 9.8%, 7.0%, a nd 5.8%, respectively (chi(2) = 3.4, p > 0.05). CONCLUSION: It would a ppear that a preterm twin birth does not to any significant extent aff ect the gestational duration of a subsequent singleton pregnancy.