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Risk of congenital anomalies higher in babies born to mothers with endometriosis
For babies born to people with endometriosis, there is a small but significant increased risk of congenital anomalies, often called birth defects, according to new research in CMAJ (Canadian Medical Association Journal).
Endometriosis is an often-painful chronic inflammatory condition where endometrial-like tissue grows outside the uterus. It affects 1 in 10 females of reproductive age and can affect fertility.
The study included data from ICES on more than 1.4 million births in Ontario, of which 33 619 were infants of patients with endometriosis. A total of 2120 (6.3%) infants with any type of congenital anomaly were born to a patient with endometriosis compared with 77 094 (5.4%) born to people without the condition.
Endometriosis was associated with an increased risk of cardiovascular, gastrointestinal, genital, and musculoskeletal anomalies as well as neoplasms and tumours, which could be only partially attributed to fertility treatment.
The authors note that the risk is still small.
“Although we observed modest relative increases in risk, the absolute risk of congenital anomalies for infants born to patients with endometriosis remained low, because congenital anomalies are uncommon,” writes Bailey Milne, Queen’s University, Kingston, Ontario, with coauthors.
A practice article published in the same issue of CMAJ describes a patient with chronic endometriosis that caused severe organ damage.
“These articles underscore the imperative for timely diagnosis, effective treatment, and greater awareness of endometriosis because of its potentially serious sequelae,” write Drs. Olga Bougie, associate professor in the Department of Obstetrics and Gynaecology, University of Toronto, and Catherine Varner, CMAJ deputy editor, in a related editorial. “However, endometriosis remains misunderstood, underrecognized, and undertreated in Canada.”
The editorial calls for a community-of-practice model for endometriosis care, with support for primary care physicians to diagnose and manage uncomplicated cases.
“Addressing these challenges requires a fundamental shift toward coordinated, evidence-based, and patient-centred care,” the authors write.
For clinical guidance on endometriosis, CMAJ published a review article, Diagnosis and management of endometriosis, in 2023.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Associate Professor Luk Rombauts is the Director of Clinical Research at Monash IVF.
"The results of this well-conducted Canadian study in women with endometriosis suggest that this debilitating condition may have impacts that go beyond the patient. The study reports that certain congenital abnormalities were more common in babies born to women with endometriosis.
While these congenital abnormalities were only mildly increased and not a cause for major concern, they do indicate that we are still learning more about this condition every day. It is reassuring to see that since the National Action Plan for Endometriosis was announced by the Federal Government in 2017, Australia has taken the world lead in new endometriosis initiatives, focusing on better-funded research and health care delivery."
Professor Carol Bower is a Senior Principal Research Fellow at The Kids Research Institute investigating the causes and effects of birth defects
"This is a large, well-conducted cohort study of over a million births in Ontario, Canada. 2.3% were associated with endometriosis; and there was small (16%) increased risk of congenital anomalies in this group, compared with patients without endometriosis.
A small proportion of the increased risk was associated with interventions to treat infertility in the endometriosis group, such as IVF, which itself is a risk factor for congenital anomalies, but there remains an independent increased risk associated with endometriosis.
This study does not provide information on how endometriosis may cause congenital anomalies or how to prevent them occurring.
Many of the congenital anomalies that showed an increase in risk are amenable to treatment (eg cleft palate, hypospadias, some heart and musculoskeletal anomalies).
Patients with endometriosis are unlikely to be deterred from proceeding with pregnancy because of the increased risk of congenital anomalies. Nevertheless, it is important that they are counselled about the possibility, along with information about preventive strategies for pregnancy generally, such as folic acid to prevent spina bifida and avoidance of alcohol in pregnancy to prevent Fetal Alcohol Spectrum Disorder."
Dr Kelsi Dodds is a National Endometriosis Clinical and Scientific Trials (NECST) Postdoctoral Fellow at Adelaide University
"This is a large population-based study using approx.15 years’ worth of medical record data in Ontario, Canada. This type of data is very robust. The major conclusion – a small (~0.9%) increase in risk of congenital birth defects in babies born to women with endometriosis – is accurate based on the available data. However, there are several limitations to the data, and the conclusion should be met with caution.
For example, the groups being compared – “endometriosis” versus “no endometriosis” – were based on diagnosis. Endometriosis is notoriously underdiagnosed, so it is plausible that many women with “no endometriosis” had undiagnosed endometriosis. If the true incidence of endometriosis was known, it is possible that the purportedly increased risk may disappear.
Also, the use of fertility treatments in the endometriosis group was significantly higher than no endometriosis, which cannot be ruled out as a contributing factor to the purportedly increased risk. Further, many of the “abnormalities” listed are not life threatening and rather cosmetic.
In line with the Editorial, these findings are not a cause for alarm, rather a call to action. Efforts to diagnose endometriosis earlier could mitigate disease progression and thus possibly reduce the potential increased burden of congenital abnormalities.
Australia is at the forefront of investing in endometriosis research and education for better health outcomes. This includes public and health professional education for better awareness and diagnosis/specialist referral, non-invasive and accessible diagnostics such as ultrasound, and by providing multi-disciplinary healthcare clinics. Australians should be aware that endometriosis could be associated with an increased risk of congenital abnormalities, but often these conditions do not impact the long-term health and wellbeing of their children."
Dr Tal Jacobson is a Clinical Senior Lecturer at the University of Queensland and a Consultant Gynaecologist at Eve Health and Mater Hospital Brisbane
"This interesting paper highlights an increased risk of congenital abnormalities in the babies of patients who have previously been diagnosed with endometriosis compared to those who have not previously been diagnosed with endometriosis.
It is based in Ontario, Canada and includes nearly 1.5 million births between 2006 and 2021. That is an impressive study size and should be taken seriously.
It is important to realise that the increase in risk is only very small. The risk of abnormalities in babies is increased from 5.4% in women without endometriosis to 6.3% in women with endometriosis.
The abnormalities that are more associated with having endometriosis include cleft palate, hypospadias and pulmonary artery stenosis.
The authors sought to adjust for other factors known to be associated with increased risk of congenital abnormalities such as patient age at delivery, income, diabetes, high blood pressure, smoking, alcohol use, substance use, obesity and other comorbidities. They excluded multiple births. They also adjusted for the possible effects of fertility treatments such as IVF.
The authors suggest that the reasons may be to do with increased inflammation in endometriosis patients affecting embryological pathways.
This retrospective population-based observational study does have some limitations. The diagnosis of endometriosis was based on hospital procedure codes; the outcomes regarding congenital anomalies used hospital databases. These are prone to error and bias.
There was an unexpectedly low prevalence of women with endometriosis (2.3% instead of an expected 10%). The average age of patients with endometriosis was 33.4 at the time of birth compared to 30.7 in those without endometriosis.
They were also much more likely to have conceived with IVF (10.6% compared to 1.5%). The authors did adjust for age and IVF usage, and the contributions of these confounding factors were considered to be small.
I would conclude from this study that there is a possible small increased risk of congenital abnormality if you have endometriosis. The risk increases from 54 per thousand births in those without endometriosis to 63 per thousand births in those with endometriosis.
This result should not deter anyone with endometriosis from having a baby, but it should inspire more research into this association to try and determine the cause and develop potential interventions."
Melanie McGrice is an Advanced Accredited Practising Dietitian with a Masters degree in nutrition. She is a founding member of the Early Life Nutrition Coalition.
"This study adds to growing evidence that endometriosis is linked to a small but meaningful increase in the risk of congenital anomalies. In Australia, we’re leading the way with multidisciplinary care, where dietitians play a key role alongside medical teams. Nutrition support before and during pregnancy can help optimise maternal health and improve outcomes for both mother and baby."
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