Pre-conception counseling for women with structural or functional heart disease.
Directing the frequency of multidisciplinary maternal-fetal and cardiology surveillance during pregnancy.
Determining absolute contraindications to pregnancy.
Hemodynamic Crisis
Pregnancy induces a 50% increase in blood volume and cardiac output. The mWHO scale predicts which diseased hearts will catastrophically decompensate under this unique, 9-month physiologic stress test.
Unoperated ASD/VSD, repaired Tetralogy of Fallot, most arrhythmias. Mortality < 1%.
Class II-III
Mild LV impairment, Hypertrophic cardiomyopathy, Marfan syndrome without aortic dilation.
Class III & IV (High to Extreme Risk)
Class III
Mechanical valves, Systemic Right Ventricle, Fontan circulation, Unrepaired cyanotic heart disease. High risk of severe morbidity.
Class IV
Pulmonary Arterial Hypertension (PAH), Severe symptomatic Aortic/Mitral stenosis, Marfan with aorta >45mm, LV Ejection Fraction <30%. Pregnancy contraindicated.
Section 3
Pearls/Pitfalls
Notorious Pitfalls
Pulmonary Arterial Hypertension (PAH) carries a maternal mortality rate of 20-50%. If a Class IV patient presents pregnant, termination is strongly medically advised.
Mechanical valves (Class III) are incredibly difficult to manage. Warfarin is highly teratogenic, but switching to heparin exponentially increases the risk of maternal mechanical valve thrombosis and death. It strictly requires a highly specialized cardio-obstetrics team.
Peri-partum cardiomyopathy is a uniquely unpredictable, often catastrophic heart failure that develops in the last month of pregnancy or first few months postpartum, regardless of prior baseline.
Section 4
Next Steps
Management Triggers
01
Class I: Routine prenatal care with 1-2 cardiology visits.
02
Class II: Delivery at local hospital is generally safe; cardiology review every trimester.
03
Class III: Requires delivery at a highly-resourced tertiary care center with cardiothoracic surgery on standby. Bi-monthly cardiology/MFM visits.
04
Class IV: If patient refuses termination, requires extreme surveillance. Planned early delivery (often via planned C-section in a cardiac OR) with intensive care team.
Section 5
Evidence Appraisal
European Society of Cardiology
2018 ESC Guidelines for the management of cardiovascular diseases during pregnancy.
Regitz-Zagrosek V et al. • Eur Heart J.. 2018;The definitive societal guideline that operationalized the Modified WHO classification as the gold standard predictive metric over legacy systems like the CARPREG score.
Section 6
Literature
Evolution of Maternal Cardiology
Historically, women with complex congenital heart disease did not survive into childbearing age. Surgical advancements created an entirely new demographic of pregnant women with repaired (but not normal) hearts, necessitating the creation of the mWHO index.
