A new study, led by researchers at the London School of Hygiene & Tropical Medicine (LSHTM), in collaboration with partners at the University of Oxford, showed the health risks associated with weight gain during pregnancy.

Not gaining enough weight during pregnancy doubles a woman’s risk of low birthweight newborns, gestational diabetes mellitus and being born “too small” compared to their peers. Similarly, excessive weight gain was associated with a more than 50% higher risk for pregnancy induced high blood pressure and emergency caesarean section.

The study, published in The American Journal of Clinical Nutrition, tracked over 15,000 weight records from over 3,300 pregnant women across Brazil, Kenya, Pakistan, South Africa, Thailand and the United Kingdom.

Professor Eric Ohuma, Professor of Medical Statistics and Epidemiology at LSHTM and senior author on the study, said: “More than 50% of women in our study did not gain enough weight during pregnancy, based on the current standards and guidelines available. These women and their babies are at significantly more risk of health problems or complications. There needs to be better follow up care, providing appropriate monitoring and nutritional advice to ensure women can sufficiently manage their weight during pregnancy to prevent devastating outcomes. 

“Measuring weight gain during pregnancy has been standard clinical practice for decades, however the majority of studies have been in high-income countries. With limited data from low- and middle- income countries, there is no global consensus for the recommended weight a woman should gain for a safe and health pregnancy.

“Our study challenges the current approach to monitoring weight, which is assessed against total weight gained throughout pregnancy or per trimester. However, we propose that assessment of appropriate weight gain should be judged according to exact gestational age, not just at the end. This approach will help identify potential risks earlier, offer opportunity for advise on weight management during pregnancy and prevent complications related to insufficient or excessive weight gain during pregnancy.

“Our research makes a significant contribution to the understanding of maternal weight gain and its association with adverse outcomes, providing valuable insights and practical implications for clinicians and policymakers in managing weight gain and improving health outcomes for both mother and baby.

“The World Health Organization is currently working towards developing global standards for weight gain according to BMI class that can be used to monitor women during pregnancy. In addition, the planned work will provide appropriate thresholds to be used for screening and identifying those gaining insufficient or excessive weight gain and therefore requiring further monitoring.

“By providing new evidence on the optimal weight gain range associated with reduced risks of adverse maternal and newborn outcomes, this study fills an important knowledge gap. These findings have significant implications for maternal and child health policies and interventions, particularly in settings with large populations of reproductive-age women.”

Publication

Jabin N, Malla L, Otieno G, Ismail LC; INTERBIO-21st Consortium; Papageorghiou AT, Kennedy SH, Villar J, Ohuma EO. Association between gestational age-specific weight gain in pregnancy and risk of adverse perinatal outcomes: a secondary analysis of the INTERBIO-21st Fetal Study. American Journal of Clinical Nutrition. DOI: 10.1016/j.ajcnut.2025.04.012.