Heart disease in pregnancy

• Pregnancy asks the heart to pump 40 to 50 percent more blood, so a woman with known heart disease needs planning before she conceives.
• Cardiovascular disease is the leading cause of pregnancy-related death in the United States, and heart disease is the commonest cause of maternal death in Western countries. ^[2]
• Every woman with cardiac disease should have her maternal risk graded before and during pregnancy with the modified World Health Organization (mWHO) classification; this beats older risk scores. ^[1]
• Mechanical valve prostheses carry the highest risk in pregnancy, driven by the need for anticoagulation. ^[1]
• Peripartum cardiomyopathy (PPCM) is heart failure with systolic dysfunction starting late in pregnancy or after delivery; most cases are diagnosed postpartum. ^[1]
• Shared decision-making by a pregnancy heart team, from pre-conception through the first year postpartum, improves outcomes. ^[1]

By the end of this page you should be able to:

1. Explain the cardiovascular and haematological changes of pregnancy and why they matter for a woman with heart disease.
2. Grade maternal cardiac risk with the mWHO classification and know who needs an expert centre.
3. Assess and manage mitral and aortic stenosis, regurgitant lesions and prosthetic valves in pregnancy.
4. Recognise and initiate treatment for peripartum cardiomyopathy, including bromocriptine.
5. Choose and monitor anticoagulation for a pregnant woman with a mechanical valve, and plan delivery safely.

Cardiovascular disease is the primary cause of pregnancy-related mortality in the United States. The burden spans hypertensive disorders, hypercholesterolaemia, myocardial infarction, cardiomyopathies, arrhythmias, valvular, thromboembolic, aortic and cerebrovascular disease, and risk rises with advancing maternal age and pre-existing comorbid conditions such as diabetes mellitus and hypertension. ^[2]

Hypertensive disorders of pregnancy are the commonest medical complication of pregnancy, affecting 5 to 10 percent of pregnancies worldwide, and remain a major cause of maternal, fetal and neonatal morbidity and mortality. Fetal risks in pre-eclampsia include intrauterine growth restriction in about 25 percent of cases, pre-maturity in about 27 percent, and intrauterine death in about 4 percent. ^[1]

This page covers the physiological stress of pregnancy, risk stratification, valve disease, peripartum cardiomyopathy and anticoagulation in mechanical valves. Congenital lesions and cardiomyopathies other than PPCM are summarised where they alter management in pregnancy.

Pregnancy induces cardiovascular changes to meet the metabolic demands of the mother and fetus. Plasma volume and cardiac output rise to a maximum of 40 to 50 percent above baseline by 32 weeks of gestation, with 75 percent of that increase achieved by the end of the first trimester. The rise is achieved first by an increase in stroke volume, then by a gradual increase in heart rate. Atrial and ventricular diameters enlarge while ventricular function is normally preserved. Systemic and pulmonary vascular resistances fall. ^[1]

Maternal cardiac dysfunction impairs uteroplacental flow and worsens fetal outcome, so even a compensated heart lesion can decompensate late in pregnancy. Haemodynamic stress continues into labour and the early postpartum period: uterine contractions, pain, anxiety, bleeding, anaesthesia and uterine involution all cause surges in blood pressure and cardiac output. ^[1]

Pregnancy is also a hypercoagulable state with increased thromboembolic risk. Liver enzyme systems, glomerular filtration and plasma volume change, protein binding decreases and serum albumin falls, so the pharmacokinetics of many drugs are altered; doses often need re-titration. ^[1]

• A lesion that is asymptomatic when she is not pregnant (for example moderate mitral stenosis) can become symptomatic in the second trimester when cardiac output has risen. ^[1]
• The risk does not end with delivery: the first two weeks postpartum carry a high risk of pulmonary oedema and thrombosis. ^[1]
• Natriuretic peptide levels track events: an NT-proBNP above 128 pg/mL at 20 weeks is predictive of cardiac events later in pregnancy. ^[1]

Hypertension in pregnancy is defined as systolic blood pressure of 140 mmHg or more and/or diastolic 90 mmHg or more; 160/110 mmHg or more is severe. Four varieties exist: pre-existing, gestational, pre-eclampsia (gestational hypertension with significant proteinuria, defined as 0.3 g or more per 24 hours) and pre-existing hypertension with superimposed gestational hypertension. Pre-eclampsia is more frequent in first pregnancies, multiple pregnancy, antiphospholipid syndrome, and with pre-existing hypertension, renal disease or diabetes; it is a common cause of prematurity and intrauterine growth restriction and is a recognised predictor of heart failure in women with heart disease. ^[1]

An sFlt1 to placental growth factor ratio of 38 or less can be used to exclude development of pre-eclampsia within the next week when pre-eclampsia is suspected. Women at high or moderate risk should take 100 to 150 mg of aspirin daily from week 12 to weeks 36 to 37. ^[1]

The modified World Health Organization (mWHO) classification is the most accurate system for assessing maternal cardiac risk in pregnancy and should be used before conception and re-applied at each visit. ^[1]

Risk is further refined with the CARPREG and ZAHARA predictors (for example, prior cardiac events, NYHA functional class above II, systemic ventricular dysfunction, left heart obstruction, anticoagulation) and with disease-specific estimates. ^[1]

Practical rules from the same guideline: ^[1]

• Fertility treatment is contraindicated in mWHO class IV and should be carefully considered in class III or in any anticoagulated woman.
• Women with mWHO class IV conditions should be counselled against pregnancy; if pregnancy occurs, termination should be discussed.
• Pre-eclampsia is a predictor of heart failure in women with heart disease.
• The mWHO class is probably more appropriate for developed than developing countries, so risk should be individualised.

Every woman with known cardiac or aortic disease who wishes to conceive needs timely, individualised pre-pregnancy counselling that considers not only the medical condition but also emotional, cultural and ethical context. At minimum: ECG, echocardiography, an exercise test, and (for aortic pathology) complete aortic imaging. A pregnancy exercise capacity above 80 percent is associated with a favourable outcome. ^[1]

Valvular heart disease in women of childbearing age is often rheumatic, particularly in low- and middle-income countries. Stenotic lesions are poorly tolerated because the pregnancy-related rise in cardiac output increases transvalvular gradients by about 50 percent, mainly between the first and second trimesters. ^[1]

Mild mitral stenosis is generally well tolerated. Heart failure occurs in one-third of pregnant women with a valve area under 1.0 cm2 and in one-half of those with a valve area up to 1.5 cm2, most often in the second trimester, even if she was asymptomatic beforehand. A valve area under 1.5 cm2 is considered clinically significant. Sustained atrial fibrillation is rare (under 10 percent) but can precipitate heart failure and thromboembolism. Mortality is 0 to 3 percent in Western countries and higher in low- and middle-income countries. ^[1]

Management principles: ^[1]

• Severity is assessed by planimetry (pressure half-time is less reliable in pregnancy); mean gradient and pulmonary artery pressure assess haemodynamic consequence.
• Prophylactic beta-1-selective blockers (metoprolol or bisoprolol) and activity restriction are used when symptoms or a systolic pulmonary artery pressure of 50 mmHg or more develop. Diuretics are added if symptoms persist (avoid high doses); if paroxysmal or permanent atrial fibrillation, left atrial thrombus or prior embolism, anticoagulate with heparin or a vitamin K antagonist.
• Percutaneous mitral commissurotomy is preferred when intervention is needed before pregnancy (even asymptomatic, and when the valve area is under 1.0 cm2), and during pregnancy only after 20 weeks and in women in NYHA class III or IV, or with systolic pulmonary artery pressure of 50 mmHg or more, despite optimal medical therapy. ^[1]
• Labour and delivery: vaginal delivery is favoured in mild stenosis and in significant stenosis without pulmonary hypertension; caesarean section is generally considered in women in NYHA class III or IV, with pulmonary hypertension, or after failed commissurotomy.

Offspring risks: prematurity 20 to 30 percent, intrauterine growth restriction 5 to 20 percent, fetal death 1 to 5 percent. ^[1]

The main cause is bicuspid aortic valve followed by rheumatic disease. Heart failure is rare (under 10 percent) in moderate aortic stenosis and in women asymptomatic before pregnancy, but occurs in about one in four symptomatic patients. Even with severe stenosis, pregnancy is often well tolerated when prior exercise tolerance is normal. Mortality is now rare with careful management. Women with bicuspid aortic valve have low dissection risk if the aortic diameter is under 50 mm. Pre-term birth, growth restriction and low birth weight occur in 20 to 25 percent of offspring of mothers with moderate or severe stenosis. ^[1]

Management: counsel symptomatic patients with severe stenosis (or asymptomatic patients with impaired left ventricular function or abnormal exercise test) against pregnancy and operate pre-pregnancy. In pregnancy, percutaneous valvuloplasty or valve replacement after early caesarean delivery is reserved for severe refractory symptoms or life-threatening cases. ^[1]

Mitral and aortic regurgitation can usually be managed conservatively: fluid overload is treated medically. Heart failure occurs in 20 to 25 percent of women with moderate or severe rheumatic mitral regurgitation; intrauterine growth restriction occurs in 5 to 10 percent of offspring. Surgery (preferably repair) is performed pre-pregnancy; acute severe regurgitation with refractory heart failure may need surgery during pregnancy, with delivery first if the fetus is mature. Vaginal delivery with epidural and a shortened second stage is advisable. ^[1]

Secondary tricuspid regurgitation is usually left-sided or pulmonary hypertension driven; severe symptomatic tricuspid regurgitation with right ventricular dysfunction increases maternal risk but can usually be managed medically. ^[1]

A mechanical valve offers excellent durability but the need for anticoagulation makes pregnancy high risk: in the ROPAC registry, event-free pregnancy with a live birth occurred in only 58 percent of women with a mechanical valve, versus 79 percent with a bioprosthesis and 78 percent with heart disease but no valve prosthesis. A UK study reported favourable outcome for mother and baby in only 28 percent of cases. ^[1]

Valve thrombosis risk with VKAs throughout pregnancy is 0 to 4 percent. With low-molecular-weight heparin (LMWH) throughout pregnancy, with anti-Xa monitoring and dose adjustment according to peak levels, valve thrombosis occurs in 4.4 to 8.7 percent; several thromboses still occurred with peak anti-Xa levels within the 1.0 to 1.2 IU/mL target. Using LMWH only in the first trimester carries a similar 5.8 to 7.4 percent thrombosis rate. Substituting UFH or LMWH for VKAs in weeks 6 to 12 almost eliminates embryopathy, because heparin does not cross the placenta. ^[1]

Maternal and fetal costs of anticoagulation: ^[1]

• VKAs in the first trimester are associated with increased miscarriage (28.6 percent versus 9.2 percent with LMWH or UFH). ^[1]
• Total fetal loss with VKA is 32.5 percent; with low-dose VKA, 13.4 to 19.2 percent. ^[1]
• Embryopathy occurs in 0.6 to 10 percent with first-trimester VKA, and is dose-dependent: 0.45 to 0.9 percent with low-dose warfarin. ^[1]
• Foetopathy (ocular and central nervous system abnormalities) occurs in 0.7 to 2 percent with VKA in the second and third trimesters; vaginal delivery on VKA is contraindicated because of fetal intracranial bleeding. ^[1]
• Low-dose aspirin added to VKA or heparin has no proven benefit in preventing valve thrombosis and is associated with significantly more maternal bleeding, including fatal events.

For women with mechanical valves, pregnancy must be managed in an expert centre by a pregnancy heart team. ^[1]

Dosing and monitoring thresholds from the 2018 ESC pregnancy guideline: ^[1]

• Low-dose VKA is warfarin under 5 mg per day, phenprocoumon under 3 mg per day, or acenocoumarol under 2 mg per day; high-dose VKA is above these. ^[1]
• LMWH starting dose is 1 mg per kg body weight for enoxaparin, or 100 IU per kg for dalteparin, twice daily subcutaneously; adjusted daily until the anti-Xa target is reached, then weekly. ^[1]
• Anti-Xa targets: 1.0 to 1.2 IU/mL for mitral or right-sided valves, and 0.8 to 1.2 U/mL for aortic valves, measured 4 to 6 hours post-dose; pre-dose (trough) anti-Xa above 0.6 IU/mL may be considered. ^[1]
• Target INR for mechanical prostheses follows the usual prosthetic valve recommendations.

Strategy by trimester: ^[1]

• Continue VKA until pregnancy is achieved. In the first trimester, continuation of VKA should be considered if the warfarin dose needed is under 5 mg per day after full information and consent; otherwise discontinue VKA between weeks 6 and 12 and replace with intravenous UFH (aPTT at least 2 times control) or LMWH twice daily with anti-Xa adjustment. ^[1]
• During the second and third trimesters until the 36th week, VKA is recommended if a low dose suffices (class I), and should be considered at high dose (class IIa). LMWH with anti-Xa monitoring may be considered at high VKA dose after full information and consent (class IIb).
• Anticoagulation changes should be implemented in hospital. Monitoring during pregnancy is weekly or every two weeks depending on the regimen (INR for VKA; anti-Xa for LMWH), with monthly echocardiography.
• Before delivery, replace LMWH with intravenous UFH (aPTT at least 2 times control) at least 36 hours before planned delivery; stop UFH 4 to 6 hours before delivery and restart 4 to 6 hours after if there is no bleeding. Plan the timing of delivery to keep anticoagulation safe. ^[1]

LMWH is not recommended when weekly anti-Xa monitoring and dose adjustment cannot be guaranteed. Fibrinolysis in pregnancy carries a fetal loss of about 30 percent with surgery; tissue plasminogen activator does not cross the placenta but experience is limited. ^[1]

PPCM is heart failure due to left ventricular systolic dysfunction, occurring towards the end of pregnancy and in the months after delivery, with most cases diagnosed postpartum. Predisposing factors include multiparity, African ethnicity, smoking, diabetes, pre-eclampsia, malnutrition, advanced age and teenage pregnancy. Potential mechanisms include inflammation, angiogenic imbalance, a biologically active 16 kDa prolactin fragment and soluble fms-like tyrosine kinase 1. ^[1]

• Left ventricular ejection fraction is usually under 45 percent; the ventricle may not be dilated. ^[1]
• Presentation is typical heart failure, often acute, with breathlessness, orthopnoea, oedema and sometimes ventricular arrhythmia or cardiac arrest. ^[1]
• Echocardiography is the imaging modality of choice; initial LVEF under 30 percent, left ventricular end-diastolic diameter of 6.0 cm or more, or right ventricular involvement predict worse outcome. ^[1]
• Careful history is needed to exclude other causes of heart failure in pregnancy (pre-eclampsia or eclampsia pulmonary oedema, pulmonary embolism, pneumonia, myocardial infarction). ^[1]

Mortality ranges from 2.0 percent in a German cohort to 12.6 percent in a South African cohort (at 6 months); a Turkish cohort reported 24 percent mortality at 24 months. If LVEF has not recovered to above 50 to 55 percent, subsequent pregnancy should be discouraged; even with normalised function, counselling is required because of recurrence risk. ^[1]

Acute or subacute heart failure is managed according to acute heart failure guidelines, by an interdisciplinary team with a pre-specified algorithm. Practical points specific to pregnancy: ^[1]

• Avoid foetotoxic agents: ACE inhibitors, angiotensin receptor blockers, ARNI, mineralocorticoid receptor antagonists and atenolol.
• Treat pulmonary congestion with loop diuretics (and thiazides if needed); avoid diuretics without congestion because of reduced placental flow.
• Hydralazine and nitrates appear safe in the presence of hypertension or severe dysfunction. Beta-blockers (beta-1 selective) should be cautiously introduced and uptitrated.
• Beta-adrenergic agonists are toxic in PPCM and should be avoided; levosimendan may be the preferred inotrope. Cardiogenic shock or inotrope dependence warrants early transfer for mechanical circulatory support and urgent caesarean delivery.
• High resting heart rate predicts adverse outcome; ivabradine may be useful when the woman is not pregnant or breastfeeding.
• Relapse has been seen after rapid tapering, so treatment continues at least 6 months after full recovery, then is tapered gradually.

Bromocriptine (2.5 mg once daily for at least 1 week in uncomplicated cases; 2.5 mg twice daily for 2 weeks then 2.5 mg once daily for 6 weeks when EF is under 25 percent or in cardiogenic shock) added to standard heart failure therapy may improve recovery and outcome. It must always be accompanied by anticoagulation with heparin, at least in prophylactic doses, because of the thrombotic risk. The BOARD mnemonic (Bromocriptine, Oral heart failure therapies, Anticoagulants, vasoRelaxing agents, Diuretics) summarises acute PPCM care. ^[1]

Devices: an implantable defibrillator is not implanted early because recovery is common; a wearable cardioverter-defibrillator may be used for 3 to 6 months when LVEF is under 35 percent. ^[1]

Dilated cardiomyopathy encompasses a number of conditions resulting in left ventricular dilatation and dysfunction, including prior viral infection, drugs and ischaemia; about 50 percent of cases are idiopathic, of which 20 to 35 percent are hereditary, with prevalence of idiopathic dilated cardiomyopathy around 1 in 2500. Pregnancy is poorly tolerated in some women, with the potential for irreversible deterioration; maternal mortality predictors are NYHA class III or IV and ejection fraction under 40 percent, with highly adverse risk when ejection fraction is under 20 percent, with mitral regurgitation, right ventricular failure, atrial fibrillation or hypotension. ^[1]

Pre-pregnancy care includes switching or stopping contraindicated heart failure drugs (ACE inhibitors, angiotensin receptor blockers, ARNI, mineralocorticoid receptor antagonists and ivabradine) before conception under close clinical and echocardiographic monitoring, while beta-blockers are continued and switched to beta-1-selective agents. Relapse has been observed after rapid tapering, so treatment should continue for at least 6 months after full recovery of left ventricular function followed by gradual tapering. ^[1]

Pulmonary arterial hypertension is an mWHO class IV condition, with a predicted maternal cardiac event rate of 40 to 100 percent. Women should be counselled against pregnancy, and if pregnancy occurs termination should be discussed. ^[1]

Most supraventricular arrhythmias are well tolerated and fall in mWHO class II, but ventricular tachycardia is class III and an arrhythmia can precipitate heart failure (for example in mitral stenosis). Management mirrors that of the non-pregnant patient but with fetal safety in mind: beta-1 selective blockers are preferred, non-vitamin K oral anticoagulants are contraindicated throughout pregnancy, and in AF associated with native valve disease immediate anticoagulation is required with heparin at therapeutic doses in the first and last trimesters and a vitamin K antagonist with the usual target INRs (or LMWH) in the second. The choice between cardioversion and rate control with digoxin or beta-blockers depends on the severity of the underlying valve disease and on maternal tolerance. ^[1]

Marfan syndrome and other heritable thoracic aortic diseases carry a moderate aortic dilatation (40 to 45 mm) in mWHO class III and severe dilatation (above 45 mm) in class IV; such women should be counselled against pregnancy. Women with a bicuspid aortic valve have a low risk of dissection if the aortic diameter is under 50 mm. Modern pre-pregnancy management is guided by aortic size index rather than diameter alone, and follow-up imaging intervals are set by the pregnancy heart team. ^[1]

Most findings are those of the underlying lesion plus the superimposed pregnancy load. Dyspnoea, orthopnoea, palpitations, syncope (especially positional), new murmur or a thromboembolic event in a young woman should prompt cardiac assessment. Differential diagnoses of new breathlessness include pulmonary embolism, anaemia, infection, asthma, and pre-eclampsia-related pulmonary oedema; none is excluded by a normal ECG. ^[2]

• Echocardiography is the cornerstone; transthoracic imaging suffices for most lesions; transoesophageal imaging is used for valves and prostheses, and a pregnancy heart team interprets results. ^[1]
• NT-proBNP above 128 pg/mL at 20 weeks predicts later cardiac events. ^[1]
• ECG, chest radiography (with abdominal shielding), blood tests for anaemia and renal function, and oxygen saturation are adjuncts. ^[1][2]

Vaginal delivery is favoured for most women with heart disease; caesarean section is reserved for obstetric indications or specific lesions (for example severe symptomatic aortic stenosis, failed commissurotomy). Time the delivery to keep anticoagulation safe: ideally with a pregnancy heart team in an expert centre for higher-risk classes. Early postpartum monitoring (24 to 72 hours) is essential because fluid mobilisation and thrombosis risk peak then. ^[1][2]

• Heart failure and pulmonary oedema, especially in the second trimester and early postpartum. ^[1]
• Arrhythmia (atrial fibrillation, ventricular tachycardia). ^[1]
• Thromboembolism and valve thrombosis (mechanical valves). ^[1]
• Fetal: miscarriage, pre-term birth, growth restriction, fetal loss as quantified under each lesion. ^[1]
• Maternal death: cardiovascular disease is the primary cause of pregnancy-related mortality in the United States. ^[2]

• Rheumatic mitral stenosis remains the dominant lesion in many low- and middle-income settings, so proficiency in bedside and transthoracic echocardiography is critical. ^[1]
• Closed commissurotomy and balloon valvuloplasty may be available where open-heart surgery is not; arrange early transfer when surgery on bypass is unavailable locally. ^[1]
• Mortality from severe mitral stenosis is higher in low- and middle-income countries, and mechanical circulatory support is usually absent, so risk counselling and earlier intervention matter most. ^[1]

• Pregnancy raises cardiac output by 40 to 50 percent, so heart disease must be planned for before conception. ^[1]
• mWHO grades maternal risk better than older scores; classes III and IV need expert-centre care, and class IV is a contraindication to pregnancy. ^[1]
• Mitral stenosis is the most important lesion that is unmasked by pregnancy; it is significant when the valve area is under 1.5 cm2. ^[1]
• Regurgitant lesions usually tolerate pregnancy if left ventricular function is preserved. ^[1]
• A mechanical valve makes pregnancy high risk (about 58 percent event-free live birth); VKA is the safest anticoagulant for the mother but carries fetal risk by trimester. ^[1]
• LMWH for a mechanical valve needs strict anti-Xa monitoring: 1.0 to 1.2 IU/mL for mitral or right-sided valves, 0.8 to 1.2 U/mL for aortic valves. ^[1]
• Peripartum cardiomyopathy presents late in pregnancy or postpartum with LVEF under 45 percent; most deaths and diagnoses occur after delivery. ^[1]
• Bromocriptine 2.5 mg daily (or 2.5 mg twice daily tapering in severe disease) is added to heart failure therapy with mandatory heparin anticoagulation. ^[1]
• Stopping foetotoxic drugs (ACE inhibitors, ARBs, ARNI, MRA, atenolol) before conception is a central counselling point. ^[1]
• Cardiovascular disease is the primary cause of pregnancy-related mortality in the United States. ^[2]

Cardiovascular and pregnancy topics worth reading next include hypertensive disorders of pregnancy, venous thromboembolism in pregnancy, valvular heart disease and anticoagulation, peripartum cardiomyopathy, and heart failure. Plain-text links will be added once those topics are published.