Prenatal anaemia and risk of postpartum haemorrhage: A cohort analysis of data from the Predict-PPH study

Background: Most previous clinical studies investigating the connection between prenatal anaemia and postpartum haemorrhage (PPH) have reported conflicting results. Objectives We examined the association between maternal prenatal anaemia and the risk of PPH in a large cohort of healthy pregnant women in five health institutions in Lagos, Southwest Nigeria. Methods This was a prospective cohort analysis of data from the Predict-PPH study that was conducted between January and June 2023. The study enrolled n = 1222 healthy pregnant women giving birth in five hospitals in Lagos, Nigeria. The study outcome, WHO-defined PPH, is postpartum blood loss of at least 500 milliliters (mL). We used a multivariable logistic regression model with a backward stepwise conditional approach to examine the association between prenatal anaemia of increasing severity and PPH while adjusting for confounding factors. Results Of the 1222 women recruited to the Predict-PPH study between January and June 2023, 1189 (97·3%) had complete outcome data. Up to 570 (46.6%) of the enrolled women had prenatal anaemia while 442 (37.2%) of those with complete follow-up data had WHO-defined PPH. After controlling for potential confounding factors, maternal prenatal anaemia was independently associated with PPH (adjusted odds ratio = 1.37, 95% confidence interval: 1.05–1.79). We also recorded no statistically significant differences in postpartum blood losses between women without anaemia and across the different categories of women affected by anaemia (P = 0.349). Conclusion Prenatal anaemia regardless of severity increases the risk of PPH in our study cohort. Our findings have significant policy implications, including the need to lower the prevalence of anaemia in resource-constrained settings like Nigeria by implementing population-level nutritional and educational interventions to improve dietary intake and lower recurrent infections and inflammation among women of reproductive age.