Study Question: Is polycystic ovary syndrome (PCOS) associated with an increased risk of severe maternal morbidity (SMM)?

Summary Answer: PCOS is modestly associated with an increased risk of SMM, independent of fertility treatment use.

What is Known Already:

Women with PCOS are at higher risk of pregnancy complications, such as hypertensive disorders and gestational diabetes. Obesity & chronic hypertension are known risk factors for adverse pregnancy outcomes. However, data on PCOS and SMM—a composite indicator including maternal mortality and prolonged hospital stay—are limited.

Study Design, Size, Duration:

• Design: Population-based cohort study
• Duration: October 2006 – February 2021
• Setting: Ontario, Canada
• Sample:
  1. 492,147 pregnancies with PCOS diagnosis
  2. 1,104,081 without PCOS
• Participants, Materials, Methods:
  1. PCOS definition: Physician billing code for PCOS or hirsutism + irregular menses
  2. Outcome: Validated composite SMM during pregnancy or up to 42 days postpartum
• Analysis: Modified Poisson regression for adjusted relative risks (aRR), stratified by conception mode:
  1. Unassisted
  2. Infertility without treatment
  3. Ovulation induction/IUI (OI/IUI)
  4. IVF/ICSI

Main Results:

1. Demographics:
   1. PCOS group older (32.1 vs 29.9 years)
   2. More obesity (23.8% vs 18.7%)
2. SMM rates:
   1. PCOS: 2.4 per 100 births
   2. Non-PCOS: 2.2 per 100 births
   3. Overall aRR: 1.06 (95% CI 1.03-1.08)
3. Chronic hypertension subgroup: aRR 1.23 (95% CI 1.10-1.37)
4. By conception mode:
   1. Unassisted: aRR 1.03 (95% CI 1.01-1.06)
   2. Infertility without treatment: aRR 1.11 (95% CI 1.05-1.17)
   3. OI/IUI: aRR 1.13 (95% CI 0.97-1.32) (NS)
   4. IVF/ICSI: aRR 1.00 (95% CI 0.90-1.12) (NS)

Limitations: Retrospective design, potential outcome misclassification, and residual confounding due to administrative data reliance.

Wider Implications: PCOS modestly increases SMM risk independent of fertility treatment. Clinicians should consider this in risk assessment and management planning during pregnancy.

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