Maternal and perinatal outcomes of pregnancy in patients with cardiac disease according to the modified World Health Organization classification: systematic review and meta-analysis

OBJECTIVE: This study aimed to investigate the rates of obstetrical and maternal outcomes in individuals with congenital or acquired cardiac disease according to the modified World Health Organization classification. DATA SOURCES: This was a systematic review and meta-analysis. Medline, CINAHL, Cochrane Library, and Scopus databases were searched electronically up to August 2025. STUDY ELIGIBILITY CRITERIA: We included prospective and retrospective studies on pregnancy outcomes in individuals with cardiac disease reported according to the modified World Health Organization classification. METHODS: Quality assessment of the included studies was performed using the Newcastle-Ottawa Scale for cohort studies. A random-effects model with restricted maximum likelihood estimation was used to pool proportions, accounting for between-study heterogeneity. The study was registered with the PROSPERO database (CRD42024543896). RESULTS: In all, 32 studies were included in the meta-analysis, encompassing 95,400 pregnancies in individuals with cardiac disease. The rate of cardiac adverse events progressively increased from 2.9% (95% confidence interval, 1.5-4.4) in modified World Health Organization Ito 50.8% (95% confidence interval, 40.9-60.7) in modified World Health Organization IV. Similar trends were observed for admission to the intensive care unit and maternal death, which reached 7.3% (95% confidence interval, 3.4-11.1) in modified World Health Organization IV. Among obstetrical outcomes, the rates of hypertensive disorders of pregnancies were found to be higher in the lower-risk groups, decreasing from 10.6% (95% confidence interval, 6.1-15.0) in modified World Health Organization I to 2.0% (95% confidence interval, 0.7-4.6) in modified World Health Organization IV. Other outcomes, including stillbirth, pre-term birth, and small for gestational age, were more frequent in the high-risk groups. Similar trends were observed for neonatal outcomes, with higher rates of admission to the neonatal intensive care unit in modified World Health Organization IV (47.8% [95% confidence interval, 14.4-81.2]) than in modified World Health Organization (7.4% [95% confidence interval, 2.9-11.9]) and higher rates of congenital heart disease in the newborn in modified World Health Organization IV (13.5% [95% confidence interval, 4.3-22.7]) than in modified World Health Organization I (2.8% [95% confidence interval, 0.7-6.3]). CONCLUSION: Pregnancy in individuals with cardiac disease is associated with a high risk of maternal, obstetrical, and neonatal complications that increases across modified World Health Organization classes. The modified World Health Organization classification identifies individuals at progressively higher risk of both cardiovascular and perinatal adverse outcomes, supporting its role in clinical risk stratification and counseling.