Relationship between antenatal haematologic biomarkers and postpartum haemorrhage among pregnant women in Nigeria

Abstract Background: Anaemia in pregnancy is a common condition associated with adverse maternal outcomes, including postpartum haemorrhage (PPH). However, the temporality of this relationship remains poorly understood, as most studies rely on haemoglobin values measured at delivery, making it difficult to distinguish cause from consequence. Objective : To examine the association between haematologic and iron-related biomarkers measured at 36 weeks’ gestation and the risk of PPH. Methods: We conducted a secondary analysis of the IVON trial, a multicentre randomized controlled trial comparing intravenous versus oral iron therapy among pregnant women with moderate to severe anaemia in Nigeria. We included 787 women with biomarker data at 36 weeks and recorded estimated blood loss at delivery. Haemoglobin, serum ferritin, transferrin saturation, and platelet count were analysed. Risk ratios (RRs) and 95% confidence intervals (CIs) were estimated using log-binomial or Poisson regression, adjusting for relevant sociodemographic and clinical covariates. Missing data were handled using multiple imputation. False discovery rate control was applied to account for multiple testing. Results : The prevalence of anaemia was 76% at 36 weeks and 58% at delivery. The incidence of PPH was 13%. Haemoglobin concentration at 36 weeks was not significantly associated with PPH risk (adjusted RR: 0.92; 95% CI: 0.78, 1.08). Neither serum ferritin, iron deficiency, nor thrombocytopenia at 36 weeks showed statistically significant associations with PPH. In contrast, haemoglobin (RR: 0.87, 95% CI: 0.75, 0.92) and transferrin concentrations (RR: 0.52, 95% CI: 0.36, 0.75) measured at delivery were significantly associated with lower PPH risk, with every 1g/dl and 100µg/dl increase in haemoglobin and transferrin corresponding to 13% and 48% lower risk of PPH, respectively. Conclusion : Haematologic and iron biomarkers measured at 36 weeks were not significantly associated with PPH, suggesting that prenatal anaemia may not be a strong independent predictor of bleeding risk, though women on the IVON trial had been treated with Iron, and therefore most of the anaemic women were not iron deficient. Trial registration: International Standard Randomized Controlled Trial Number (ISRCTN) ISRCTN63484804 (https://doi.org/10.1186/ISRCTN63484804). Registered on: 10/12/2020