New research has revealed that prenatal testosterone exposure could differentially impact physical activity and muscle strength in boys and girls by age 7 years. Boys born to mothers with polycystic ovary syndrome showed reduced physical activity on weekends, while girls exposed to higher testosterone levels during pregnancy demonstrated lower muscle strength.
The findings, presented at the Joint Congress of the European Society for Paediatric Endocrinology (ESPE) and the European Society of Endocrinology (ESE) 2025, highlighted the sex-specific developmental effects of maternal testosterone.
Sex-Specific Effects Measured Objectively
Investigators analyzed data from 695 pregnant women with and without polycystic ovary syndrome (PCOS) in the Odense Child Cohort, measuring testosterone levels during the third trimester and assessing their children's physical activity and muscle strength at 7 years.
Boys born to mothers with PCOS were less physically active only during the weekends compared with boys born to mothers without PCOS. However, this association between maternal testosterone and lower physical activity in boys wasn't because of birth weight or maternal prepregnancy body mass index (BMI). The investigators observed 265 fewer counts per minute on weekends (P = .02) and 154 fewer counts per minute on all days (weekend and weekdays) (P = .04), whereas no association was found on weekdays.
Maternal PCOS was also associated with less moderate (beta = –6.7 minutes per day, P = .05), vigorous (beta = –6.3 minutes per day, P = .03) and moderate-vigorous physical activity (beta = –12 minutes per day, P = .03) on weekends.
Among girls, the relationship was different. Maternal PCOS wasn't associated with physical activity engagement. However, one nmol/L increase in maternal free testosterone (FT) was associated with an 8.5 N/kg bodyweight decrease in isometric muscle strength (P = .003).
Novel Research Methodology
The research represented a methodologic advancement in studying prenatal hormone effects on childhood development. Lead study author Camilla Viola Palm emphasized the study's innovative approach:
"While other studies have looked at testosterone levels during pregnancy and child physical activity by questionnaires, we are the first to objectively assess this association, using an accelerometer to measure movements and activity over 7 days, and to investigate boys and girls separately."
The study expanded on previous findings from the same research group, which had demonstrated that children aged 5 years had lower grip strength when their mothers had higher levels of testosterone during the third trimester. In addition, the investigators found that prenatal exposure to higher testosterone levels was associated with more body fat in 7-year-old boys.
Potential Long-term Health Implications
Dr. Palm noted the potential health consequences of the findings:
"Maternal prepregnancy health conditions, like PCOS, may transgenerationally affect the physical activity of boys. A reduction of physical activity outside weekdays, where you have more free choice of nonactivity, may increase the risk of future obesity and cardiovascular disease (CVD) in these boys."
She also highlighted that "[t]here is only little data on boys regarding PCOS-related metabolic and CVD risk, as PCOS is a female condition by definition." PCOS typically affects up to 13% of women of reproductive age.
Future Research Directions
The investigators plan to extend their analysis to determine if these effects persist beyond childhood. "The team will next assess whether these children, exposed to PCOS and higher testosterone levels in the womb, continue to have reduced physical activity into adolescence. We want to investigate whether prenatal PCOS and testosterone exposure influence long-term health outcomes like obesity, blood pressure, and type 2 diabetes," said Dr. Palm.
The ongoing work benefits from the extensive Odense Child Cohort, which provided clinical data of children from birth until 18 years of age.
This longitudinal research may reveal critical connections between prenatal hormone exposure and lifelong health outcomes, potentially informing preventive interventions for children born to mothers with PCOS.
