Two-thirds of pregnancies involve weight gain outside recommended pregnancy weight ranges, linked to complications including preterm birth and neonatal intensive care admissions, research shows.
Analysis of 1.6 million women found only 32 per cent gained the recommended amount of weight during gestation, with 23 per cent below and 45 per cent above guidelines.
Gestational weight gain (GWG) refers to the combined growth of mother and baby during pregnancy.
The research reviewed 40 observational studies from five World Health Organization regions between 2009 and 2024.
Lead researchers Helene Teede and Rebecca Godstein say findings reinforce the need for international standards alongside lifestyle support and public health measures.
The researchers concluded: “Our findings inform and support the need for optimised, evidence-based WHO international GWG reference standards based on individual patient data, applicable across the full BMI range in contemporary and diverse global populations.
“This will build on and improve current recommendations and are essential to underpin multi-level support to improve the health of mothers and babies worldwide.”
Current guidelines from the Institute of Medicine are based on data from predominantly white women in high-income countries during the 1980s.
These do not reflect ethnically diverse populations or environmental factors driving global weight trends.
Around half (53 per cent) of participants had healthy pre-pregnancy BMI (body mass index, a measure of weight relative to height), with others classified as below (6 per cent), above (19 per cent) or obese (22 per cent).
Weight gain below recommendations was linked to lower risk of caesarean delivery and large babies but higher risk of preterm birth, small babies, low birth weight and respiratory distress.
Conversely, gaining above recommended ranges increased risks of caesarean delivery, hypertensive disorders (high blood pressure complications), large babies and neonatal intensive care admission, while lowering risks of preterm birth and small babies.
Similar patterns emerged when Asian BMI categories were applied in studies from that region.
In a linked editorial, Annick Bogaerts and Dominika Osicka said wide variation across BMI categories and regions challenges the “black and white logic” behind many clinical guidelines.
They argue for a more nuanced focus on weight gain patterns, underlying determinants and personalised, non-punitive counselling.
They wrote: “Without comprehensive, life course public health strategies, the obesity epidemic will continue across generations.
“Governments and (inter)national agencies must act now to support women’s health before, during and after pregnancy, ensuring that the next generation inherits the opportunity not the risk.”
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