London School of Hygiene & Tropical Medicine

New research from the London School of Hygiene & Tropical Medicine has found that babies born to mothers who are overweight or obese in sub-Saharan Africa – where rates of obesity are projected to increase at an alarming rate during the next two decades – are significantly more likely to die in the first two days after their birth.

The study, published in The Lancet, is the first to shed light on the role of maternal obesity in neonatal death (during the first 28 days of life) in developing countries.

Lead author, Dr Jenny Cresswell, said: "Sub-Saharan Africa already has the highest rates of neonatal death in the world. Whilst overall levels of obesity are currently fairly low by global standards, obesity is actually a rapidly emerging problem, with 5% of women presently classed as obese."

By 2030, over a quarter of adults (almost 186 million) are predicted to be overweight in sub-Saharan Africa, and nearly a fifth of adults will be obese. Babies born to obese mothers are at increased risk of a range of complications including admission to neonatal care, macrosomia (excessive birthweight), low Apgar score, and death.

The new analysis is based on data from The Demographic and Health Surveys (DHS) from 27 countries in sub-Saharan Africa. The researchers analysed over 81 000 pregnancies involving deliveries of single babies between 2003 and 2009 to assess the risk of neonatal death by a mother’s body mass index (BMI).

The estimates suggest that babies of obese mothers had about 50% greater odds of their baby dying in the first 4 weeks of life (adjusted odds ratio 1.46) than women who were of optimum weight, even after adjusting for certain factors known to affect the risk of neonatal death including maternal age, educational level, and birth order.

This association was strongest in the first 2 days of life when the odds of neonatal death was 62% greater for obese women and 32% higher for overweight women compared with mothers of optimum weight.

The authors conclude: "This is the first time maternal obesity has been recognised as a risk factor in this setting. We now need more research to confirm the exact causes of death for these babies and a strategy to educate women in these countries about maintaining a healthy weight during pregnancy."

The findings put the global burden of obesity on reproductive health in a new perspective, where complications attributable to maternal obesity in low-income countries may far outnumber the burden seen in affluent countries.

• Listen to Dr Jenny Cresswell discussing her research in a Lancet podcast