Risk of Endometriosis, Adenomyosis and Related Symptoms Among Women Conceived by Mothers on Hormonal Contraceptives

Authors: Maria Magnus; JM. Cohen; K. Furu; HI. Hanevik

Prenatal exposure to hormonal contraceptives has been suggested to influence fetal reproductive development, but evidence on its long-term effects is limited. Whether maternal hormonal contraceptive use around conception increases the risk of endometriosis, adenomyosis, or related symptoms in female offspring remains uncertain.

This nationwide registry-based cohort study investigated whether women conceived while their mothers were using hormonal contraceptives have an increased risk of developing endometriosis, adenomyosis, or related menstrual symptoms. The study included 142,230 women born in Norway between 2004 and 2009. Participants were followed from 15 years of age for an average of four years. The analysis compared women conceived while their mothers were using hormonal contraceptives, defined as having a filled prescription within 90 days before the estimated date of conception, with those who were not. Outcomes were assessed using Cox regression after adjusting for maternal age, parity, maternal history of endometriosis or adenomyosis, immigrant status, and use of assisted reproductive technology (ART). Among the study population, 12,230 women (8.5%) were conceived while their mothers were using hormonal contraceptives. The risk per 10,000 follow-up days was 8 for endometriosis or adenomyosis, 355 for painful menstrual bleeding, 102 for heavy menstrual bleeding, and 8 for pain during intercourse.

Women conceived during maternal hormonal contraceptive use had a modestly increased risk of heavy menstrual bleeding (adjusted hazard ratio [aHR] 1.15; 95% confidence interval [CI] 1.05–1.27) and painful menstrual bleeding (aHR 1.12; 95% CI 1.06–1.18). However, there was no significant increase in the risk of endometriosis or adenomyosis (aHR 1.06; 95% CI 0.77–1.57) or pain during intercourse (aHR 1.05; 95% CI 0.74–1.48). Secondary analyses using a 60-day exposure window before conception produced similar results. The study was limited by the inability to fully account for hereditary factors related to endometriosis or adenomyosis and by the relatively short follow-up period.

Overall, women conceived while their mothers were using hormonal contraceptives had a modestly higher risk of painful and heavy menstrual bleeding but not of endometriosis, adenomyosis, or pain during intercourse.

Acetaminophen Use During Pregnancy and Children’s Risk of ADHD

Authors: Rune Lindahl-Jacobsen; A. Bauer; D. Kristensen

Studies have suggested a possible link between maternal acetaminophen use in pregnancy and ADHD risk in children, but findings remain inconclusive. Associations are limited by confounding and recall bias, and while a sibling‑controlled study found no link after adjusting for family factors, its reliability was questioned due to very low recorded exposure, raising concerns about misclassification.

This nationwide historical cohort study evaluated whether maternal acetaminophen (APAP) use during pregnancy is associated with an increased risk of attention-deficit/hyperactivity disorder (ADHD) in offspring. The study included nearly 1.85 million births in Denmark between 1994 and 2021, with children followed until 2024 for ADHD diagnoses. Analyses focused on approximately 1.64 million singleton births. Maternal APAP exposure was identified using redeemed prescription records during pregnancy, while offspring ADHD was identified through hospital diagnoses and/or ADHD medication prescriptions. Symphysis pubis dysfunction (SPD) was used as a proxy for pregnancy-related pain requiring analgesic treatment. The study used within-mother sibling comparisons and propensity score-matched analyses of firstborn children to reduce the effects of familial and indication-related confounding.

Among approximately 907,000 firstborn children, 1.5% were exposed to APAP during pregnancy. Prenatal APAP exposure was associated with an approximately 60% higher risk of ADHD (hazard ratio [HR] 1.60; 95% confidence interval [CI] 1.39–1.83). Sibling analyses showed that ADHD in one child strongly predicted ADHD in a sibling (relative risks approximately 6.6 and 6.2 by birth order), indicating an important contribution of shared familial factors. However, among siblings who differed in APAP exposure, prenatal exposure remained associated with a modest increase in ADHD risk (HR 1.36; 95% CI 1.23–1.51). Among firstborn children, maternal SPD without APAP use was associated with an increased ADHD risk (HR 1.40; 95% CI 1.25–1.58), while APAP use without SPD showed a similar increase (HR 1.57; 95% CI 1.37–1.81). Pregnancies with both SPD and APAP exposure had the highest estimated risk (HR 2.33), although the confidence interval (95% CI 0.62–8.72) included 1. Trimester-specific analyses showed significant associations throughout pregnancy, with stronger associations for later or persistent exposure. First-trimester APAP use was associated with an HR of approximately 1.46, third-trimester use with an HR of approximately 1.86, and use during all three trimesters with an HR of approximately 2.23 (95% CI 1.17–4.24). The study was limited because over-the-counter APAP use was not captured, potentially leading to exposure misclassification. Residual confounding and incomplete identification of milder ADHD cases may also have resulted in underestimation of the association.

Overall, maternal acetaminophen use during pregnancy was associated with an increased risk of ADHD in offspring, with the strongest associations observed for later or persistent use during pregnancy.

ESHRE 2026, July 5^th-8^th, London, UK.