By PPH Foundation
A woman’s weight may not be the first thing that comes to mind when thinking about postpartum haemorrhage (PPH), but research suggests that maternal weight can be relevant to pregnancy and childbirth outcomes. As the number of women entering pregnancy with overweight or obesity increases, understanding how body weight may intersect with PPH is becoming increasingly important for maternal care.
Dr. Frederick Kireki Omanwa, Consultant Obstetrician and Gynaecologist, KOGS President and Senior Lecturer in the Department of Obstetrics and Gynaecology at the University of Nairobi, has previously examined the importance of maternal weight in pregnancy. In research published in Ginekologia Polska, he and colleagues noted: “A pregnant woman's weight is an extremely important factor in the course of pregnancy and delivery” (Omanwa et al., 2006).
But does having obesity mean a woman will develop PPH? Not necessarily.
The relationship is more complicated. A 2025 systematic review and meta-analysis published in The Lancet, which brought together evidence from 327 studies involving more than 847 million women, identified a body mass index of 30 kg/m² or higher as having a moderate association with PPH. The same review identified several other factors with stronger associations, including anaemia, previous PPH, caesarean birth, multiple pregnancy, placenta previa, macrosomia and shoulder dystocia (Yunas et al., 2025).
Other research has also found an association between higher BMI and PPH. A 2024 systematic review and meta-analysis reported higher odds of PPH among women who were overweight or obese compared with women of normal BMI, with the risk increasing with obesity (Zhang et al., 2024).
One possible explanation is that obesity can occur alongside conditions that themselves influence pregnancy and delivery, including gestational diabetes, hypertension, pre-eclampsia, larger babies and increased likelihood of caesarean or induced birth. These factors can alter the course of labour and may contribute to situations in which bleeding becomes more difficult to prevent or manage.
However, the evidence does not support treating obesity alone as a prediction that a woman will experience severe PPH. A 2021 systematic review of risk factors for atonic PPH, the form of PPH commonly associated with failure of the uterus to contract effectively after birth, found no clear association between obesity and atonic PPH. This is an important reminder that PPH usually results from multiple interacting factors rather than a single characteristic.
More recent evidence continues to refine this picture. A 2026 population-based study involving more than 311,000 first-time mothers found that overweight and obesity were associated with higher odds of PPH, including PPH involving blood loss of at least 1,000 mL. The association was particularly evident among women who had vaginal births. The researchers also cautioned that increasing obesity could not, by itself, explain the rise in PPH rates (2026).
For healthcare providers, the message is therefore not to label women with obesity as high-risk simply because of their weight. Instead, maternal weight should form part of a broader assessment that considers the woman's medical history, blood pressure, diabetes status, previous PPH, placental conditions, fetal size, mode of delivery and other factors.
For women, pregnancy should not become a period of shame or blame because of body weight. Antenatal care provides an opportunity to identify and manage conditions that may increase complications, while ensuring that every woman gives birth in a setting prepared to recognise and respond to PPH.
Ultimately, preventing maternal deaths from PPH is not about predicting exactly which woman will bleed. It is about ensuring that maternity teams are prepared to respond quickly when bleeding occurs. Maternal weight may be one piece of that risk picture, but preparedness, early recognition and timely treatment remain essential for every woman.
References
Omanwa, K., Zimmer, M., Tlolka, J., Wytrychowska, E., Maciejewska, J., & Dryś, A. (2006). Is low pre-pregnancy body mass index a risk factor for preterm birth and low neonatal birth weight? Ginekologia Polska, 77(8), 618–623.
Yunas, I., Islam, M. A., Sindhu, K. N., Devall, A. J., Podesek, M., Alam, S. S., et al. (2025). Causes of and risk factors for postpartum haemorrhage: A systematic review and meta-analysis. The Lancet, 405(10488), 1468–1480.
Zhang, Y., Lu, Y., Yi, X., Xia, J., Zhang, Y., Li, X., & Liu, Y. (2024). Influence of maternal body mass index on pregnancy complications and outcomes: A systematic review and meta-analysis. Frontiers in Endocrinology, 15, 1280692.
Bell, S. F., et al. (2021). Risk factors for atonic postpartum haemorrhage: A systematic review and meta-analysis. Obstetrics & Gynecology.
Sweet, L., et al. (2026). Maternal body mass index and risk of post-partum haemorrhage: A population-based study in primiparous women. Obesity Research & Clinical Practice.
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