Childhood Obesity Linked to Higher Childlessness Risk in Adulthood

Pharmacists counseling patients on weight management may want to frame the conversation around reproductive health far earlier than the point of family planning. A new cohort study of nearly 61,000 Danish women found that girls who followed a body mass index (BMI) trajectory of overweight or obesity from as young as age 6 were significantly less likely to give birth in adulthood than peers with an average childhood BMI trajectory. This association is already measurable in the mid-20s and more pronounced after 30 years of age.^1,2

“Our study highlights that an elevated BMI during childhood and adolescence may have lasting implications for reproductive health,” Jennifer Baker, PhD, head of research in lifecourse epidemiology at the Center for Clinical Research and Prevention at Copenhagen University Hospital, said in an interview with Pharmacy Times. “The lack of an association with diagnosed infertility may reflect restricted access to fertility services for females with BMI values above in vitro fertilization (IVF) thresholds in Denmark.”

What the Study Found

The population-based cohort, published in JAMA Network Open, drew on the Copenhagen School Health Records Register, which captures measured height and weight from mandatory yearly school health examinations for nearly every girl attending school in Copenhagen. Researchers followed 60,864 women born between 1950 and 1989, sorting them into 5 childhood BMI trajectories from 6 to 15 years of age: below average, average, above average, overweight, and obesity.^1,2

Across the follow-up period, around 78% of the women gave birth, at a median age of 27 years, whereas 22% remained childless. After adjusting for birth cohort and highest parental education level, women with an overweight or obesity trajectory were less likely to give birth than those with an average trajectory, with the gap widening at older reproductive ages. Women with a childhood obesity trajectory were approximately 22% less likely to give birth at ages 25 to 29 years (HR, 0.78; 95% CI, 0.72-0.86) and 42% less likely at 30 to 34 years (HR, 0.58; 95% CI, 0.52-0.66). By ages 35 to 45 years, they were 44% less likely to give birth (HR, 0.56; 95% CI, 0.46-0.67). Women with an overweight trajectory showed a similar but more moderate pattern.¹

Notably, childhood BMI trajectories were not associated with hospital-diagnosed primary or any infertility. As Baker cautioned, Danish national guidelines restrict IVF access above certain BMI thresholds, meaning women with obesity may never be referred and captured in hospital infertility diagnoses. This is a caveat pharmacists should keep in mind when interpreting the childbirth versus infertility split.^1,2

The Physiology Behind the Signal

The study was observational and cannot establish causation, but its findings align with a body of evidence on how excess adiposity affects reproductive function. Per a 2021 American Society for Reproductive Medicine (ASRM) committee opinion, obesity in women is associated with ovulatory dysfunction, reduced ovarian responsiveness to ovulation-induction agents, altered oocyte and endometrial function, and lower birth rates after IVF, though most women with obesity remain fertile. The study authors similarly point to disruption of the hypothalamic-pituitary-ovarian axis, effects on oocyte quality, and hormonal disturbances as plausible pathways.^1-3

This mechanistic context is directly relevant to counseling. The ASRM opinion notes that for women with anovulation and obesity, weight loss can improve the chance of unassisted conception and the ovulation rate in response to ovulation induction. For pharmacists fielding questions about antiobesity medications in reproductive-age patients, that framing—weight management as one modifiable input to fertility, not a guarantee—supports realistic, nonstigmatizing conversations.

“Our study contributes to understanding the relationship between obesity in childhood and reproductive outcomes, but it does not provide evidence regarding the use, effectiveness, or safety of incretin-based therapies before or during pregnancy,” Baker explained. “Medication counseling should follow current obesity and reproductive health guidelines.”

Why It Matter for Pharmacists

The scale of childhood obesity gives the findings public health weight. World Health Organization data from its European Childhood Obesity Surveillance Initiative indicate that roughly 1 in 3 primary school-aged children in the region lives with overweight or obesity. Because childhood obesity frequently persists into adulthood, pharmacists are positioned to reinforce healthy growth messaging in pediatric and family settings long before reproductive concerns surface.⁴

For pharmacists counseling patients with obesity who are planning or postponing pregnancy, the takeaway is timing. Person-first, life-course counseling, paired with attention to medication considerations such as contraindications of certain anti-obesity agents in pregnancy, may add value years before a patient walks into a fertility clinic.¹

Baker expanded on this notion plainly. “Our findings do not demonstrate that weight loss improves fertility and should not change current recommendations to optimize metabolic health before conception to reduce maternal and pregnancy-related risks,” she wrote.

REFERENCES

1. Pedersen DC, Aarestrup J, Bjerregaard LG, et al. Early life BMI trajectories and associations with childbirth and infertility among women. JAMA Netw Open. 2026;9(8):e2626893. doi:10.1001/jamanetworkopen.2026.26893

2. Overweight and obesity in childhood associated with increased risk of childlessness in adulthood, finds study of almost 61,000 women. News Release. European Association for the Study of Obesity; EurekAlert! August 4, 2026. Accessed August 5, 2026. https://www.eurekalert.org/news-releases/1138705

3. Practice Committee of the American Society for Reproductive Medicine. Obesity and reproduction: a committee opinion. Fertil Steril. 2021;116:1266-85. Accessed August 5, 2026. https://www.asrm.org/practice-guidance/practice-committee-documents/obesity-and-reproduction-a-committee-opinion-2021/

4. Childhood obesity in the European region remains high: new WHO report presents latest country data. News Release. World Health Organization Regional Office for Europe. Released November 8, 2022. Accessed August 5, 2026. https://www.who.int/europe/news/item/08-11-2022-childhood-obesity-in-european-region-remains-high--new-who-report-presents-latest-country-data