Risk factors analysis and a scoring system proposal for the prediction of retained placenta after vaginal delivery

Retained placenta (RP) is an obstetric complication of third stage of labour. We aimed to evaluate risk factors for RP and to propose a scoring system in order to predict this potentially fatal disorder.

This was a retrospective case-control study, comparing women with RP after vaginal delivery (≥ 24 weeks of gestation) and women with regular placental separation. Data were collected from January 2007 to October 2017, in two 2nd level University Hospitals. Eligibility was limited to singleton pregnancies in vertex presentation with no major foetal anomaly. A nomogram was developed to predict RP risk.

Among 22,749 women who delivered vaginally, 138 (0.6%) had RP. RP was directly related with previous uterine curettage (OR = 1.92, 95% CI 1.04-3.54, p = 0.04) and labour induction with prostaglandins (OR = 4.29, 95% CI 1.83-10.02, p = 0.001), while vaginal spontaneous delivery (OR = 0.03, 95% CI 0.01-0.15, p = 0.0001) and higher Apgar score at 1 min (OR = 0.5, 95% CI 0.33-0.76, p = 0.001) were inversely related to RP. Our predictive model showed an overall diagnostic accuracy of 0.803.

RP is associated with several maternal, pregnancy, foetal and placental risk factors. The development of a new scoring system, with a high predictive power, able to identify the risk of RP, could be a useful tool for physicians in order to promptly face this life-threatening condition.