Early term birth is associated with the risk of preterm and recurrent early term birth in women with 3 consecutive deliveries

Background: We assessed the association of early term at first birth (ETB) with the risk of preterm birth (PTB) and ETB in women with 3 consecutive deliveries. Methods: We conducted a retrospective cohort study of all women with 3 consecutive singleton births at a single institute from 1994 to 2013. The risk of PTB (<37 weeks), spontaneous PTB and ETB (37−38 weeks) in the 3^rd delivery was explored. Results: Of 49,259 women delivered in our center during the study period, 4038 met inclusion criteria. The rate for subsequent PTB, spontaneous PTB and recurrent ETB in the 3^rd delivery significantly increased as the number of prior ETBs increased. The order of a single prior ETB in one of the first two deliveries was differently associated with the risk of complications in the 3^rd delivery, which was higher when the prior ETB was more recent to the third delivery. Conclusion: A history of ETB is associated with the risk of future PTB and recurrent ETB. The risk is related to the number and order of prior ETBs.