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Maternal obesity increases type 1 diabetes risk in offspring, study shows

BMJ 2015; 350 doi: (Published 28 April 2015) Cite this as: BMJ 2015;350:h2252
  1. Susan Mayor
  1. 1London

Overweight and obesity among women increases the risk of type 1 diabetes in their offspring even when neither parent has diabetes, shows a nationwide cohort study of more than 1.2 million children in Sweden.

The results, published in Diabetologia,1 indicate that efforts to reduce overweight and obesity in women before and during pregnancy might reduce the incidence of type 1 diabetes in children of parents without diabetes. The prevalence of type 1 diabetes is increasing in most countries.

The researchers followed a cohort of 1 263 358 children born in Sweden between 1992 and 2004. They tracked individual linked records for each child from the date of their birth until a diagnosis of type 1 diabetes, emigration, death, or the end of the follow-up period in 2009. Information for each child was compared with data on their mother’s body mass index (BMI) during the first trimester of the pregnancy that resulted in each child’s birth.

Type 1 diabetes was diagnosed in 5771 of the children during the study period. Among children of parents who didn’t have diabetes, having a mother who was obese during pregnancy (BMI≥30) was associated with an increase in risk of developing type 1 diabetes of a third, when compared with children of mothers whose BMI was in the normal range (incident rate ratio 1.31 (95% confidence interval 1.20 to 3.40); P for trend 0.0005).

Further analysis showed that this increased risk of type 1 diabetes with maternal obesity in pregnancy was found only in children of parents without diabetes. The risk of a child developing type 1 diabetes was greatly increased if the mother (incidence rate ratio 3.17 (2.80 to 3.58)) or father (incidence rate ratio 5.27 (4.74 to 5.86)) had type 1 or type 2 diabetes, but this risk did not increase further with maternal obesity in pregnancy.

“This nationwide cohort study demonstrates that paternal and maternal diabetes and first trimester maternal obesity are associated with increased risks of type 1 diabetes in the offspring,” wrote the researchers, led by Tahereh Moradi, of the Karolinska Institute, Stockholm. They added, “A novel finding in this study is that high maternal BMI in the first trimester of pregnancy was only associated with an increased risk of type 1 diabetes in offspring of parents without diabetes.”

They concluded, “Prevention of overweight and obesity in women of reproductive age may contribute to a decreased incidence of type 1 diabetes.”


Cite this as: BMJ 2015;350:h2252


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