Table 1.

Modified World Health Organization classification of maternal cardiovascular risk

	mWHO I	mWHO II	mWHO II–III	mWHO III	mWHO IV
Diagnosis (if otherwise well and uncomplicated)	•Small or mild – pulmonary stenosis – patent ductus arteriosus – mitral valve prolapse •Successfully repaired simple lesions -atrial or ventricular septal defect -patent ductus arteriosus -anomalous pulmonary venous drainage •Atrial or ventricular ectopic beats, isolated	•Unoperated atrial or ventricular septal defect •Repaired tetralogy of Fallot •Most arrhythmias (supraventricular arrhythmias) •Turner syndrome without aortic dilatation	•Mild left ventricular impairment (EF >45%) •Hypertrophic cardiomyopathy •Native or tissue valve disease not considered WHO I or IV (mild mitral stenosis, moderate aortic stenosis) •Marfan or other HTAD syndrome without aortic dilatation •Aorta <45 mm in bicuspid aortic valve pathology •Repaired coarctation •Atrioventricular septal defect	•Moderate left ventricular impairment (EF 30–45%) •Previous peripartum cardiomyopathy without any residual left ventricular impairment •Mechanical valve •Systemic right ventricle with good or mildly decreased ventricular function •Fontan circulation if otherwise the patient is well and the cardiac condition uncomplicated •Unrepaired cyanotic heart disease •Moderate mitral stenosis •Severe asymptomatic aortic stenosis •Moderate aortic dilatation −40–45 mm in Marfan syndrome or other HTAD −45–50 mm in bicuspid aortic valve -Turner syndrome ASI 20–25mm/m2 -tetralogy of Fallot <50 mm •Ventricular tachycardia	•Pulmonary arterial hypertension •Severe systemic ventricular dysfunction (EF <30% or NYHA class III–IV) •Previous peripartum cardiomyopathy with any residual left ventricular impairment •Severe mitral stenosis •Severe symptomatic aortic stenosis •Systemic right ventricle with moderate or severely decreased ventricular function •Severe aortic dilatation ->45 mm in Marfan syndrome or other HTAD ->50 mm in bicuspid aortic valve -Turner syndrome ASI >25 mm/m2 -tetralogy of Fallot >50 mm •Vascular Ehlers–Danlos •Severe (re)coarctation •Fontan with any complication
Risk	No detectable increased risk of maternal mortality and no/mild increased risk in morbidity	Small increased risk of maternal mortality or moderate increase in morbidity	Intermediate increased risk of maternal mortality or moderate to severe increase in morbidity	Significantly increased risk of maternal mortality or severe morbidity	Extremely high risk of maternal mortality or severe morbidity
Maternal cardiac event rate	2.5–5%	5.7–10.5%	10–19%	19–27%	40–100%
Counselling	Yes	Yes	Yes	Yes: expert counselling required	Yes: pregnancy contraindicated: if pregnancy occurs, termination should be discussed
Care during pregnancy	Local hospital	Local hospital	Referral hospital	Expert center for pregnancy and cardiac disease	Expert center for pregnancy and cardiac disease
Minimal follow-up visits during pregnancy	Once or twice	Once per trimester	Bimonthly	Monthly or bimonthly	Monthly
Location of delivery	Local hospital	Local hospital	Referral hospital	Expert center for pregnancy and cardiac disease	Expert center for pregnancy and cardiac disease

ASI = aortic size index; EF = ejection fraction; HTAD = heritable thoracic aortic disease; mWHO = modified World Health Organization classification; NYHA = New York Heart Association; WHO = World Health Organization.