Rates of and factors associated with recurrence of preterm delivery

Context Information about risk of recurrent preterm delivery is useful to clinicians, researchers, and policy makers for counseling, generating etiologic leads, and measuring the related public health burden. Objectives To identify the rate of recurrence of preterm delivery in second pregnancies, factors associated with recurrence, and the percentage of preterm deliveries in women with a history of preterm delivery. Design and Setting Population-based cohort study of data from birth and fetal death certificates from the state of Georgia between 1980 and 1995. Subjects A total of 122 722 white and 56 174 black women with first and second singleton deliveries at 20 to 44 weeks' gestation. Main Outcome Measure Length of gestation (categorized as 20-31, 32-36, or greater than or equal to 37 weeks) at second delivery compared with length of gestation at first delivery, by age and race. Results Most women whose first delivery was preterm subsequently had term deliveries. Of 1023 white women whose first delivery occurred at 20 to 31 weeks, 8.2% (95% confidence interval [CI], 6.6%-10.1%) delivered their second birth at 20 to 31 weeks and 20.1% (95 % CI, 17.7%-22.8%) at 32 to 36 weeks. Of 1084 comparable black women, 13.4% (95% CI, 11.4%-15.6%) delivered at 20 to 31 weeks and 23.4% (95% CI, 20.9%-26.1%) delivered at 32 to 36 weeks. Among women whose first delivery occurred at 32 to 36 weeks, all corresponding rates were lower than those whose first birth was at 20 to 31 weeks; the rates of second birth at 20 to 31 weeks were substantially lower (for white women, 1.9% [95% CI, 1.7%-2.2%]; for black women, 3.8% [95% CI, 3.4%-4.2%]). Compared with women aged 20 to 49 years at their second delivery, women younger than 18 years had twice the risk of recurrence of delivery at 20 to 31 weeks. Of all second deliveries at 20 to 31 weeks, 29.4% for white women and 37.8% for black women were preceded by a preterm delivery. Conclusions Our data suggest that recurrence of preterm delivery contributes a notable portion of all preterm deliveries, especially at the shortest gestations.