摘要Background:Cesarean section (CS) is an independent risk factor for placenta accreta.Some researchers think that the timing of primary cesarean delivery is associated with placenta accreta in subsequent pregnancies.The aim of this study was to investigate the risk of placenta accreta following primary CS without labor,also called primary elective CS,in a pregnancy complicated with placenta previa.Methods:A retrospective,single-center,case-control study was conducted at Peking University Third Hospital.Relevant clinical data of singleton pregnancies between January 2010 and September 2017 were recorded.The case group included women with placenta accreta who had placenta previa and one previous CS.Control group included women with one previous CS that was complicated with placenta previa.Maternal age,body mass index,gestational age,fetal birth weight,gravity,parity,induced abortion,the rate of women received assisted reproductive technology,other uterine surgery,and primary elective CS were analyzed between the two groups.Results:The rate of primary elective CS (90.1％ vs.69.9％,P ＜ 0.001) was higher,and maternal age was younger (32.7 ± 4.7 years vs.34.6 ± 4.0 years,P ＜ 0.001) in case group,compared with control group.Case group also had higher gravity and induced abortions compared with the control group (both P ＜ 0.05).Primary CS without labor was associated with significantly increased risk of placenta accreta in a subsequent pregnancy complicated with placenta previa (odds ratio:3.32;95％ confidential interval:1.68-6.58).Conclusion:Women with a primary elective CS without labor have a higher chance of developing an accreta in a subsequent pregnancy that is complicated with placenta previa.