Risk for Preterm and Very Preterm Delivery in Women Who Were Born Preterm

To evaluate whether women who themselves were born preterm are at increased risk of preterm delivery and, if so, whether known maternal complications of preterm birth such as hypertension or diabetes explain this risk. We conducted a population-based cohort study of all women born preterm (51,148) and term (823,991) in Québec, Canada, between 1976 and 1995; after frequency matching 1:2 preterm to term, we examined the relationship of preterm birth between women and their offspring. The study included 7,405 women who were born preterm (554 before 32 weeks of gestation and 6,851 at 32-36 weeks of gestation) and 16,714 women born term, who delivered 12,248 and 27,879 newborns, respectively. Overall, 14.2% of women born before 32 weeks of gestation, 13.0% of 32-36 weeks of gestation, and 9.8% of those born term delivered prematurely at least once during the study period, including 2.4%, 1.8%, and 1.2%, respectively, who delivered very preterm (both P