Original studyBMJ Mental Health, 2026Read the paper →
Obesity in pregnancy is becoming more common, and it brings well-known risks such as gestational diabetes and complications during labour. Women living with obesity are also more likely to experience depression. A new UK study suggests that a mother’s low mood in pregnancy may matter more for her child’s early emotional and behavioural development than her blood sugar.
Researchers at King’s College London followed up 462 children whose mothers had taken part in UPBEAT, a UK trial of a diet and physical activity programme for pregnant women with obesity. The study appears in BMJ Mental Health. The children were about three and a half years old when assessed, and just under half were boys.
The trial recruited pregnant women with a body mass index of 30 or more between 2009 and 2014. Their depressive symptoms were recorded at about 17, 27 and 34 weeks of pregnancy, and blood tests measured blood sugar, inflammation and a marker of how well the placenta was working. Four in 10 of the mothers followed up lived in the most deprived fifth of areas.
Children’s difficulties were measured with the Strengths and Difficulties Questionnaire, completed by parents or carers. It covers emotional symptoms, conduct problems, hyperactivity and trouble getting on with other children, and a total score of 16 or more marks a child as high risk. The placental marker is a protein whose low levels point to a placenta that may pass fewer nutrients and less oxygen to the baby.
In all, 52 children, or 11.3%, scored in the high-risk range, about twice the 5.3% the authors cite from British norms for this age. Boys were more affected than girls, at 14.7% against 8%, and about one in five boys had high scores for hyperactivity or conduct problems. Mothers of high-risk children tended to be younger, to earn less and to be less likely to hold a degree.
When the pregnancy factors were modelled together, more depressive symptoms and lower placental function were each linked to a higher chance of a high-risk score. Inflammation, blood sugar and gestational diabetes showed no direct link, and neither did how severe the mother’s obesity was. Both links held after allowing for income, education and deprivation, and for the mother’s depressive symptoms when her child was assessed.
A separate analysis grouped children by their pattern of difficulties. About 8% showed mainly outward behaviour problems such as hyperactivity and poor conduct, while 4.1% showed mainly emotional and peer problems. Children in the first group were heavier for their age and had larger waists than children without these difficulties, and both groups were fussier eaters.
The study has clear limits. It was observational, so it cannot show that depression or lower placental function cause later difficulties, and behaviour was reported by parents rather than also by teachers or clinicians. Many families did not return for the follow-up, and those who did were older, better off and more often white than the original group.
Shared genes, family circumstances, diet and activity after birth could also play a part, and it is not yet known whether these early patterns last. Even so, the researchers suggest that screening for depression and placental function in pregnancies affected by obesity may help to reduce later difficulties for children.
