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Birth Defect Risk Marginally Higher in Infants of Mothers with Endometriosis, Study Finds

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Endometriosis Linked to Slightly Higher Risk of Birth Defects, Large Study Finds

A major population-based study in Ontario, Canada, has uncovered a statistical association between maternal endometriosis and a modestly increased risk of congenital anomalies in infants. Published in the Canadian Medical Association Journal (CMAJ), the research analyzed over 1.4 million births spanning October 2006 to March 2021.

"Infants of mothers with endometriosis had a 16% higher relative risk of any congenital anomaly."

Key Findings

The study compared 33,619 births to mothers diagnosed with endometriosis against a larger control group of mothers without the condition.

Risk Breakdown

  • Relative Risk: After adjusting for other factors, the risk of any congenital anomaly was 16% higher in the endometriosis group.
  • Absolute Risk: The rate of anomalies was 6.3% among infants of mothers with endometriosis, compared to 5.4% among those without.

Specific Anomalies Noted

Researchers observed elevated relative risks for several conditions:

  • Unspecified cleft palate: 52% higher risk
  • Hypospadias: 47% higher risk
  • Pulmonary artery stenosis: 41% higher risk
  • Undescended testicles: 36% higher risk
  • Cardiovascular and genital anomalies, as well as neoplasms/tumors: 23–27% higher risk

Contributing Factors

The analysis adjusted for maternal age, diabetes, high blood pressure, smoking, alcohol and substance use, obesity, and income.

Role of Fertility Treatment

  • Invasive treatments like IVF or ICSI accounted for approximately 11% of the observed association.
  • Notably, 10.6% of women with endometriosis conceived via IVF, compared to just 1.5% of women without the condition.
  • Other fertility treatments (e.g., ovulation induction, intrauterine insemination) did not appear to mediate the relationship.

Independent Link

The association between endometriosis and congenital anomalies persisted even after accounting for IVF.

Study Limitations

Experts noted several important caveats. Dr. Tal Jacobson pointed out that only 2.3% of mothers in the study had a diagnosed endometriosis—far below the estimated population prevalence of ~10%. This discrepancy, combined with potential errors in hospital databases, suggests significant underdiagnosis.

Dr. Kelsi Dodds cautioned that this underdiagnosis could mean the true risk of birth defects associated with the condition might be lower than reported. The study's authors also acknowledged potential unmeasured confounders, including:

  • Disease stage
  • Specific treatment cycles
  • Use of pain medications