Influence of parity on first trimester endovascular trophoblast invasion

ObjectiveTo assess the effect of parity on endovascular trophoblastic invasion in early pregnancy.DesignObservational study.SettingTeaching hospital.Patient(s)Healthy women at 10–14 weeks of gestation.Intervention(s)Surgical termination of pregnancy for nonmedical reasons.Main Outcome Measure(s)Products of conception were blindly examined histologically with regard to the extent of decidual endovascular trophoblast invasion.Result(s)Samples were obtained from 20 nulliparous and 10 parous women. The presence of normal intradecidual endovascular trophoblast invasion was identified with a similar frequency in both groups (P=.28). However, the proportion of decidual vessels with endovascular trophoblast invasion was significantly higher in parous women (60%) compared with nulliparous women (32%, P<.001).Conclusion(s)Endovascular trophoblast invasion in early pregnancy is more extensive in parous women who already had an uncomplicated pregnancy than in nulliparous women.