Childhood Obesity in Girls Linked to Reduced Fertility in Adulthood: JAMA

A new study published in the Journal of American Medical Association showed that girls who were overweight or obese as children were less likely to give birth in their late twenties and thirties than those with a normal body mass index.

Although the association between early-life BMI and adult fertility is yet unknown, childhood weight may have an impact on health and reproductive consequences later in life. Many prior research has relied on self-reported childhood weight or infertility, and the results have been inconsistent. Therefore, this study determined if childhood BMI trends were related to the chance of becoming pregnant and experiencing infertility as an adult.

The Copenhagen School Health Records Register in Denmark provided the data for this prospective, population-based cohort research. 60,864 women were included in the study of births, 58,148 in the analysis of primary infertility, and 63,066 in the analysis of any infertility. Trained school clinicians measured children's height and weight between the ages of six and fifteen. To determine childbearing and infertility outcomes to age 45, this study categorized patients into five BMI trajectories: below average, average, above average, overweight, and obesity. They then connected this information with Danish national registers.

60 864 women were included in the childbirth analysis of this study, of which 47 669 (78.3%) gave birth; 58 148 were included in the primary infertility analysis, of which 5381 (9.3%) were diagnosed with primary infertility; and 63 066 were included in the any infertility analysis, of which 6961 (11.0%) were diagnosed with any infertility.

Giving birth was less likely for women with a childhood obesity trajectory than for those with a typical trajectory, and this risk declined with age. In a similar vein, women who had an overweight trajectory as children had a reduced risk of delivering a birth, and this risk declined with age. There were no correlations found between primary or other types of infertility and the childhood BMI trajectories.

Overall, those with an overweight or obese BMI trajectory in childhood were less likely to have children than women with an ordinary BMI. The relationship was already visible between the ages of 25 and 29, and it got even more apparent beyond the age of 30, when many women begin attempting to conceive. Childhood BMI trajectories, on the other hand, were not consistently related to primary or secondary infertility.

Reference:

Pedersen, D. C., Aarestrup, J., Bjerregaard, L. G., Andersen, E. W., Jensen, A., Kjær, S. K., Juliusson, P. B., Rasmussen, K. M., & Baker, J. L. (2026). Early life BMI trajectories and associations with childbirth and infertility among women. JAMA Network Open, 9(8), e2626893. https://doi.org/10.1001/jamanetworkopen.2026.26893