The HAPPY study: the effects of obese pregnancy on children aged 3-5

Rebecca Reynolds, Theresia Mina, Mandy Drake, Fiona Denison, Jane Norman

Researchers in our Edinburgh clinic show that children born to obese women are more likely to have behavioural problems.

This research study is now complete

Researchers at our metabolic clinic in Edinburgh have shown that the children of very obese mothers are more likely to show behavioural problems. These results apply for obese women independent of the mother's education, class or stress levels.

Scientists looked at measurements from 116 children aged 3-5. These included measures of body size, as well as samples of spit, blood and a swab from the inside of the cheek. Children completed tests of their development, such as the 'Head Shoulders Knees Toes Test': in this, the child must complete the opposite motion from the one they are told to (if the adult tells them to touch their head, they touch their toes). Mothers also filled in a questionnaire about their child's behaviour, sleep patterns, and development.

Behaviour problems more likely

The findings from these tests show that children whose mothers were severely obese – defined as having a BMI of 40 or more - during pregnancy perform worse on tests of development, and are more likely to have behavioural problems. These include hyperactivity, anxiety, aggressive behaviour, and symptoms of attention-deficit-hyperactivity disorder (ADHD). They were also more likely to have poorer short-term memory and problem-solving skills.

Results like these are really significant. These children are about to start school, and it is important for their teachers to know that they might have problems concentrating so that they can help them learn at their full potential.

The clinic will continue looking at whether helping obese mothers with their health before and during pregnancy could help the longer term development of their children. They will also see whether trying to improve their children's health in early childhood will help solve some of these problems. 

Research papers

  • O’Reilly JR, Reynolds RM.  The Risk of Maternal Obesity to the Long Term Health of the Offspring.  Clinical Endocrinology 2013;78(1):9-16
  • Drake AJ, Reynolds RM. How and why does maternal obesity cause adverse effects in offspring in later life? Reproduction 2010; 1403:387-98.



Thanks for your interest in our research

Tommy's funds research across the UK investigating the reasons for pregnancy complications and loss. Maternal and fetal research is underfunded and we need your support to continue. There are many small and large ways you can support us, find out more here.


This study takes place in a Tommy's centre and is funded by Tommy's and the University of Edinburgh

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