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Childhood obesity is linked to weight gain during pregnancy, US study finds

BMJ 2013; 347 doi: (Published 02 October 2013) Cite this as: BMJ 2013;347:f5891
  1. Zosia Kmietowicz
  1. 1BMJ

The likelihood of a child becoming obese is linked to the amount of weight that the mother gained during pregnancy, a study has concluded.

The researchers, from Boston Children’s Hospital, Arkansas Center for Health Improvement, and Princeton University, wanted to find out whether childhood obesity was due just to conditions during pregnancy (that influence birth weight) or whether other factors shared by mother and child (such as diet and genes) had a role.

They combined two large databases of public records in Arkansas, where it is now compulsory for all public school children to have weight and height measured every other year, allowing body mass index (BMI) to be calculated. Altogether they collected data on 41 133 women and 91 045 of their children at birth and age 12 years.

The study, published in PLoS Medicine, showed that mothers gained around 14 kg in each pregnancy.1 Using a within-family design the researchers calculated that for each kilogram of weight gain during pregnancy the BMI of the child at age 12 was greater by 0.02 (95% confidence interval 0.013 to 0.031, P<0.0001).

After adjusting for birth weight this association remained significant, and the authors calculated that childhood BMI increased by 0.014 (0.006 to 0.03; P=0.0007) for every kg of weight gained by the mother.

There was a nearly linear relation between mothers’ weight gain and the risk of a child being overweight or obese. The odds ratio for overweight or obesity among children whose mothers gained more than 18 kg in pregnancy was 1.08 (1.01 to 1.15; P=0.02).

The difference between the BMI increase associated with the smallest pregnancy weight gains and that associated with the biggest was 0.43. By comparison, the estimated increase in average BMI of children in the United States since the 1970s is 2.0.

The authors acknowledged that they did not have information on the mothers’ body mass index before pregnancy and that this would have been useful. But they said that including these data would be likely to make the findings even more pronounced (because women with a higher body mass index tended to gain less weight in pregnancy).

The authors concluded that “measures to limit pregnancy weight gain may help prevent obesity in the subsequent generation.” Further research should focus on how best to advise pregnant women on managing their weight in pregnancy, they said.


Cite this as: BMJ 2013;347:f5891


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