The Preterm Prediction Study: Effect of gestational age and cause of preterm birth on subsequent obstetric outcome

OBJECTIVE: We sought to evaluate the association between prior spontaneous preterm delivery and subsequent pregnancy outcome. STUDY DESIGN: A total of 1711 multiparous women with singleton gestations w ere prospectively evaluated at 23 to 24 weeks' gestation. Prior pregnancies were coded for the presence or absence of a prior spontaneous preterm deli very. If a prior spontaneous preterm delivery had occurred, the gestation o f the earliest prior delivery (13-22, 23-27, 28-34, and 35-36 weeks' gestat ion) was recorded. Current gestations were categorized as spontaneous prete rm delivery at <28, <30, <32, <35, or <37 weeks' gestation. The risk of spo ntaneous preterm delivery in the current gestation was determined on the ba sis of the occurrence, gestational age, and cause of the earliest prior spo ntaneous preterm delivery RESULTS: The incidences of spontaneous preterm delivery before 28, 30, 32, 35, and 37 weeks' gestation were 0.8%, 1.1%, 1.9%, 5.1%, and 11.9%, respect ively. Those with a prior spontaneous preterm delivery carried a 2.5-fold i ncrease in the risk of spontaneous preterm delivery in the current gestatio n over those with no prior spontaneous preterm delivery (21.7% vs 8.8%; P l ess than or equal to.001). Gravid women with an early prior spontaneous pre term delivery (23-27 weeks' gestation) had a higher risk of recurrent spont aneous preterm delivery (27.1% vs 8.8%; P less than or equal to.001). Prior spontaneous preterm delivery was more closely associated with subsequent e arly spontaneous preterm delivery at <28 weeks' gestation (relative risk, 1 0.6) than for spontaneous preterm delivery overall (relative risk, 2.5). An early prior spontaneous preterm delivery (23-27 weeks' gestation) was most highly associated with early spontaneous preterm delivery (<28 weeks' gest ation) in the current gestation (relative risk, 22.1). The relationship bet ween prior spontaneous preterm delivery and current outcome was not as stro ng for those with a very early spontaneous preterm delivery (13-22 weeks' g estation). Prior spontaneous preterm delivery caused by preterm premature r upture of the membranes and preterm labor was significantly associated with similar outcomes in the current gestation (P < .001). CONCLUSION: Prior spontaneous preterm delivery is highly associated with re currence in the current gestation. An early prior spontaneous preterm deliv ery is more predictive of recurrence and is most highly associated with sub sequent early spontaneous preterm delivery.