MOTHERS WHO GAIN weight in between pregnancies increase the risk of stillbirths and infant deaths, according to new research.
A study involving 450,000 women has found that mothers who are a healthy weight during their first pregnancy and gain even a moderate amount of weight (around 6kg/13lbs in a woman of average height – about 5ft 4cm) between their first and second pregnancies increase the risk of their baby dying in its first year of life.
The findings show an incremental increase in the risk of stillbirth with weight gain between pregnancies, regardless of a woman’s weight during her first pregnancy. The study also found that weight loss between pregnancies reduced the likelihood of neonatal death (within 28 days of birth) in babies of overweight women.
The research, which is published in The Lancet medical journal, is based on data from the Swedish Medical Birth Register.
Professor Sven Cnattingius from the Karolinska Institutet in Stockholm said the public health implications of the study are “profound”.
Around a fifth of women in our study gained enough weight between pregnancies to increase their risk of stillbirth by 30–50%, and their likelihood of giving birth to babies who die in infancy increased by 27–60% if they had a healthy weight during their first pregnancy.
Researchers analysed more than 450,000 women who gave birth to their first and second child between 1992 and 2012 to assess the risk of stillbirth (foetal death at 28 weeks or later) and infant mortality (death within the first year of life) by a change in mother’s body mass index (BMI) between the first and second pregnancies.
Causes of death included congenital abnormalities, birth asphyxia, infections and sudden infant death syndrome (SIDS).
‘Epidemic levels’
The findings suggest that babies of mothers of average height who gained more than four BMI units (11kg/24lbs) between pregnancies had about a 50% greater risk of their baby dying in the first four weeks of life than women who were of stable weight (a BMI change from -1 to less than 1kg/m²).
This was the case even after adjustments were made for certain factors known to affect the risk of stillbirth including maternal age, educational level and smoking.
The authors suggest that increments in BMI in healthy weight women might reflect a greater increase of fat mass than in obese women, and therefore a greater risk. In contrast, overweight mothers who lost at least 6kg (13lbs) before their second pregnancy had about a 50% reduced likelihood of neonatal death.
Study co-author Eduardo Villamor, Professor of Epidemiology at the University of Michigan School of Public Health, said the prevalence of pregnant women who are overweight or obese “has reached epidemic levels”.
Our findings highlight the importance of educating women about maintaining a healthy weight during pregnancy and reducing excess weight before becoming pregnant as a way to improve infant survival.
Dr Daghni Rajasingam, a spokesperson for the Royal College of Obstetricians and Gynaecologists in the UK, said the study “adds to the evidence that being overweight or obese increases the risk of stillbirth and child mortality”.
“Women who are overweight or obese, whether planning a first pregnancy or are between pregnancies, should try to lose weight on a structured weight loss programme recommended by a healthcare professional – aiming to lose around 1kg or one to 2lbs a week. Even a small weight loss can give you and your baby significant benefits.”
Note: In the study, maternal BMI was recorded as underweight for 18.5kg/m² or less, healthy for 18.5kg/m² to 24.9kg/m², overweight for 25 kg/m² to 29.9 kg/m², or obese for 30kg/m² or over.
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