Background Retained placenta is a complication of the third stage of labour that is associated with increased rates of post-partum haemorrhage. Previous research identified risk factors related to maternal demographics and delivery related variables, but both clinical practises and patient variables have since changed. This study re-examines risk factors for manual removal of placenta (MROP) across parity.

Method This case-control study was conducted at the National Maternity Hospital in Dublin Ireland from January 2011 to Dec 2011. A chart review of all liveborn, singleton, vaginal deliveries was conducted to investigate maternal and delivery related variables in relation to retained placenta. Women were grouped based on the need for MROP as well as by parity. Statistical analysis was performed using chi square tests and odds ratios.

Results 7163 deliveries met the study criteria and 190 (2.65%) required MROP. Risk factors that were identified were parity, two or more miscarriages, previous ERPC, gestation at delivery, and oxytocin to accelerate labour. When divided based on parity, increased maternal age was a significant risk factor for primiparous patients. For both groups, MROP was associated with greater blood loss.

Conclusion These results show an increase in the rate of MROP as compared to earlier studies and identifies similar risk factors. Of note, maternal age in primiparous women and use of oxytocin are factors that have undergone change since earlier studies and may be contributing to the rise in the rates of MROP in the industrialised world.