May 11, 2026

expert reaction to study looking at association between mothers having endometriosis and children born with congenital abnormalities

A study published in the Canadian Medical Association Journal looks at an association between endometriosis in mothers and children born with congenital abnormalities.

Professor Asma Khalil, Professor of Obstetrics and Maternal Fetal Medicine at St George’s, University of London, said:

“This is a large, well-conducted population-based study involving more than 1.4 million births, and the authors have carefully adjusted for several important confounding factors, including maternal age, obesity, smoking, hypertension, diabetes, and fertility treatment.

“The study found a modest increase in the relative risk of congenital anomalies among babies born to women with endometriosis. However, it is important to emphasise that the absolute increase in risk was small. The vast majority of women with endometriosis will still have babies born without congenital anomalies.

“Importantly, this study demonstrates an association rather than proof of causation. Women with endometriosis are more likely to have other factors linked to adverse pregnancy outcomes, including subfertility, delayed childbearing, inflammation, medication exposure, and use of assisted reproductive technologies. Although the authors attempted to account for many of these factors, residual confounding is still possible.

“The findings are biologically plausible, particularly given the inflammatory and immunological pathways associated with endometriosis, but the underlying mechanisms remain uncertain. Reassuringly, the increases in risk were generally small, and for many individual anomalies the absolute numbers were very low.

“Overall, this study adds to growing evidence that pregnancies in women with endometriosis may benefit from closer antenatal attention, but it should not cause undue alarm for patients.”

‘Risk of congenital anomalies among infants of patients with endometriosis: a population based cohort study’ by Bailey Milne et al. was published in Canadian Medical Association Journal at 05:01 UK time on Monday 11 May 2026. 

DOI: 10.1503/cmaj.250439

Declared interests

Professor Asma Khalil: “Professor Asma Khalil is Professor of Obstetrics and Maternal Fetal Medicine at St George’s, University of London, and Immediate Past Vice President of the Royal College of Obstetricians and Gynaecologists. She has no relevant conflicts of interest relating to this study.”