Maternal anaemia and the risk of giving birth to a small vulnerable newborn: a cohort analysis of the WOMAN-2 trial in four countries

Abstract

Objective: To investigate the association between maternal haemoglobin concentration and the risk of small vulnerable newborn (SVN) birth. Design: Cohort analysis of data from the World Maternal Antifibrinolytic Trial-2 (WOMAN-2). Setting: Hospitals in Nigeria, Pakistan, Tanzania, and Zambia. Population: Women with moderate or severe anaemia giving birth vaginally between August 2019 and September 2023. Methods: Multivariable logistic regression analysis examining the association between maternal haemoglobin levels and SVN, adjusting for potential confounders. Outcome Measure: We defined SVN as a live- or stillborn baby born preterm (<37 weeks), low birthweight (<2500g), and/or small-for-gestational-age (birthweight <10th percentile of weight specific for sex and gestational age) Results: Among 14444 women, the median haemoglobin level was 85g/L (IQR: 77-91g/L), and the incidence of SVN was 39.5% (5703/14444). A strong inverse relationship was observed between maternal haemoglobin and SVN. Compared to women with haemoglobin 90-99g/L adjusted odds ratios for SVN were: 1.06 (95% CI: 0.97-1.16) for 80-89g/L; 1.32 (95% CI: 1.19-1.46) for 70-79g/L; 1.63 (95% CI: 1.43-1.86) for 60-69g/L; 2.33 (95% CI: 1.83-2.96) for 50-59g/L; and 2.51 (95% CI: 1.85-3.41) for <50g/L. Sensitivity analysis, including multiple pregnancies, yielded similar results. Conclusions: More severe maternal anaemia is associated with increased risk of SVN. These findings emphasise the importance of comprehensive anaemia prevention and management strategies in prenatal care and among women of reproductive age.