Congenital Heart Disease in Women of Reproductive Age

More than 3 million women of reproductive age now live with congenital heart disease worldwide, a population that has grown by 1 million since 1990 due to surgical advances that transformed fatal childhood conditions into chronic adult diseases. The CARPREG II study established that women with CHD face cardiac event risks ranging from 2.9% to 41% during pregnancy, depending on lesion complexity and ventricular function. Every woman with CHD planning pregnancy requires formal preconception risk stratification by an adult congenital heart disease specialist. 5 / Solid

The Survival Paradox

She had her VSD repaired at age 4 and was told she was cured. At 28, considering pregnancy, her cardiologist said: repaired is not the same as normal. We need to talk about what pregnancy would do to your heart.

This conversation happens with increasing frequency. Ninety percent of children born with congenital heart disease now survive to adulthood. The prevalence of CHD among women aged 15 to 45 years has increased 3 to 4 percent annually since 1994 (Drenthen et al. 2005). The result is a population of women who have never known a world without their heart condition but have also never been counseled about what that condition means for pregnancy.

The biology is unforgiving. Pregnancy increases plasma volume by 40 to 50 percent. Heart rate rises 10 to 20 beats per minute. Cardiac output climbs 30 to 50 percent above baseline. Systemic vascular resistance drops. For a structurally normal heart, these changes are physiologic adaptations. For a heart that was reconstructed in childhood, these changes are stress tests.

The problem extends beyond the heart itself. Women with CHD have residual lesions, abnormal myocardium, scarred conduction systems, and sometimes prosthetic valves that change the risk calculus entirely. A woman with a simple atrial septal defect repair may tolerate pregnancy beautifully. A woman with a Fontan circulation faces 44 percent odds of a serious cardiac event (van Hagen et al. 2018).

The CDC reports that more than 1 in 5 women with heart defects who became pregnant had not received any of the American Heart Association’s recommended preconception care in the year before conception. This gap between surgical survival and reproductive counseling represents preventable harm. 5 / Solid

The CARPREG II Framework

Risk stratification in pregnant women with heart disease required formalization. The original CARPREG score (Cardiac Disease in Pregnancy), published in 2001, identified four predictors of maternal cardiac events: prior cardiac event or arrhythmia, baseline NYHA class greater than II or cyanosis, left heart obstruction, and reduced systemic ventricular function. It was a start.

CARPREG II, published by Silversides and colleagues in 2018, refined the model using 1,938 pregnancies in women with heart disease (Silversides et al. 2018). The updated score includes ten predictors grouped into general predictors and lesion-specific predictors.

General predictors carry one point each: prior cardiac events or arrhythmias, poor functional class or cyanosis, high-risk valve disease or left ventricular outflow tract obstruction, systemic ventricular dysfunction with ejection fraction below 40 percent, no prior cardiac intervention, and late pregnancy assessment.

Lesion-specific predictors carry additional points: mechanical valve (3 points), high-risk aortopathy (2 points), pulmonary hypertension (2 points), and coronary artery disease (2 points).

The math translates to maternal cardiac event rates:

• Score 0: 2.9% risk
• Score 1: 7.5% risk
• Score 2: 14.5% risk
• Score 3: 22.5% risk
• Score 4 or higher: 41% risk

A woman with repaired tetralogy of Fallot who has good ventricular function, no prior arrhythmias, and underwent surgical evaluation before pregnancy might score 0 or 1. The same lesion with pulmonary regurgitation causing right ventricular dilation, functional limitation, and no preconception assessment might score 4. Same diagnosis. Radically different risk. 5 / Solid

The CARPREG II framework gives both patient and physician a common language. It converts intuition into probability. It also identifies which factors are modifiable before pregnancy, particularly the “late assessment” point that rewards preconception planning.

The WHO Risk Classification

The 2018 ESC Guidelines on cardiovascular disease in pregnancy established a complementary system: the modified World Health Organization (mWHO) risk classification (Regitz-Zagrosek et al. 2018). This system categorizes lesions into four classes based on expected maternal and fetal outcomes.

mWHO Class I represents minimal risk. This includes successfully repaired simple lesions such as isolated patent ductus arteriosus, repaired atrial or ventricular septal defect without residual shunt, and isolated ectopic beats.

mWHO Class II represents small increased risk. This includes unrepaired atrial or ventricular septal defects, repaired tetralogy of Fallot, and most arrhythmias.

mWHO Class III represents significantly increased risk requiring specialist care. This includes mechanical valves, systemic right ventricle, Fontan circulation, unrepaired cyanotic heart disease, and moderate left ventricular impairment.

mWHO Class IV represents pregnancy contraindicated due to extremely high risk of maternal mortality. This includes pulmonary arterial hypertension, severe systemic ventricular dysfunction (EF below 30%), Eisenmenger syndrome, severe aortic stenosis, and severe native coarctation.

Eisenmenger syndrome deserves particular attention. When pulmonary hypertension develops from a long-standing left-to-right shunt, the shunt reverses. Pulmonary vascular resistance exceeds 6 Wood units. The right ventricle pumps against fixed, elevated afterload. Pregnancy, with its increased cardiac output demands and decreased systemic vascular resistance, causes right-to-left shunting to increase, oxygen saturation to plummet, and right ventricular failure to precipitate. Maternal mortality ranges from 30 to 50 percent. Pregnancy termination itself carries 7 percent mortality in Eisenmenger syndrome.

Women don’t die from what they have. Women die from what they hold.

In this context, holding means holding onto the belief that a childhood surgery made everything normal, holding onto inadequate counseling, holding onto a healthcare system that did not connect pediatric survival to adult reproductive risk. 5 / Solid

High-Risk Lesions: The Specific Dangers

Not all congenital heart defects carry equal pregnancy risk. Understanding the hemodynamic vulnerabilities of specific lesions guides counseling.

Fontan Circulation. The Fontan operation, performed for single-ventricle physiology, connects systemic venous return directly to the pulmonary arteries without a subpulmonary ventricle. Pulmonary blood flow depends entirely on passive venous pressure. Pregnancy-induced venodilation reduces this preload. The gravid uterus compresses the inferior vena cava. The result is inadequate cardiac output at the precise moment demand is highest.

The systematic review by van Hagen and colleagues found 44 percent of women with Fontan circulation experienced maternal cardiac events during pregnancy, predominantly arrhythmias (22%) and heart failure (15%). Fetal outcomes are also compromised: live birth rates are 60 to 70 percent, with high rates of prematurity and low birth weight (van Hagen et al. 2018). 5 / Solid

Repaired Coarctation of the Aorta. Even successful repair leaves residual aortopathy. The aortic wall contains cystic medial necrosis, a structural weakness that predisposes to dissection. Pregnancy elevates blood pressure in the third trimester and dramatically increases cardiac output. Women with repaired coarctation face 5 to 10 percent risk of pregnancy-induced hypertension and 3 to 5 percent risk of aortic complications including dissection. Patch angioplasty repairs carry higher risk than end-to-end anastomosis repairs because the patch material lacks elastic properties of native aorta. Pre-pregnancy aortic imaging is mandatory.

Mechanical Heart Valves. Women with mechanical prostheses face the anticoagulation dilemma. Warfarin is teratogenic in the first trimester, causing embryopathy in 5 to 10 percent of exposed pregnancies. Heparin is safer for the fetus but associated with 4-fold higher rates of valve thrombosis and maternal death. There is no perfect strategy. The 2018 ESC guidelines recommend vitamin K antagonists throughout pregnancy for women with high thrombotic risk (older generation mechanical mitral valves, atrial fibrillation, prior thromboembolism), accepting fetal risk. For lower-risk situations, they suggest low-molecular-weight heparin in the first trimester with strict anti-Xa monitoring, then warfarin until 36 weeks. CARPREG II assigns 3 points to mechanical valves for precisely this reason.

Marfan Syndrome and Aortopathy. While not strictly CHD, many women with congenital aortic abnormalities have connective tissue disorders. Aortic root diameter above 40 mm at baseline predicts prohibitive pregnancy risk. The 2018 ESC guidelines recommend beta-blockers throughout pregnancy for Marfan patients and advise against pregnancy if aortic root exceeds 45 mm. (Regitz-Zagrosek et al. 2018) 5 / Solid

Preconception Evaluation: The Non-Negotiable Protocol

The gap between knowing risk exists and acting on that knowledge kills women. The CDC data showing that more than 20 percent of women with CHD received no preconception care represents system failure.

The preconception evaluation framework for women with CHD should include five components.

Anatomic Assessment. Echocardiography defines ventricular function, valvular lesions, and residual defects. For aortopathy, CT or MRI measures aortic dimensions at multiple levels. For complex CHD, cardiac MRI quantifies ventricular volumes and regurgitant fractions. The anatomy visible at age 4 is not the anatomy present at age 28.

Functional Capacity Testing. Cardiopulmonary exercise testing measures peak oxygen consumption (VO2 max) and ventilatory efficiency (VE/VCO2 slope). A VO2 max below 16 mL/kg/min predicts adverse pregnancy outcomes. A woman who cannot walk up two flights of stairs without dyspnea should not assume she can tolerate the hemodynamic demands of late pregnancy.

Arrhythmia Assessment. Twenty-four hour Holter monitoring or extended rhythm monitoring identifies baseline arrhythmia burden. Women with CHD have abnormal atrial tissue from surgical scars and abnormal conduction systems from ventricular surgery. Pregnancy is proarrhythmic. Identifying arrhythmia substrate before pregnancy allows prophylactic treatment.

Risk Score Calculation. Every woman with CHD deserves a formal CARPREG II score and mWHO classification documented in her medical record before conception. This is not optional.

Medication Review. ACE inhibitors, ARBs, and aldosterone antagonists are teratogenic. Amiodarone causes fetal thyroid abnormalities. Warfarin causes embryopathy. Statins are contraindicated. The medication review must happen before conception, not after the pregnancy test is positive. (Mongeon et al. 2020) 5 / Solid

Contraception and the Risk-Benefit Calculation

For women with CHD in whom pregnancy is high-risk or contraindicated, effective contraception becomes cardiac care. Yet contraceptive counseling is often inadequate.

Combined hormonal contraceptives (estrogen plus progestin) increase venous thromboembolism risk 3 to 4-fold. For women with Fontan circulation, mechanical valves, pulmonary hypertension, or history of thromboembolism, combined hormonal methods are generally contraindicated.

Progestin-only methods (implants, injections, progestin-only pills) do not carry the same thrombotic risk and are generally acceptable for most women with CHD. The levonorgestrel IUD is highly effective and avoids systemic hormonal effects almost entirely.

Copper IUDs carry no hormonal risks but may cause heavier menstrual bleeding, problematic for women on anticoagulation.

The critical point: contraception decisions for women with CHD require cardiology input. The default options offered by primary care or gynecology may be inappropriate. This represents another failure of care coordination.

For women with mWHO Class IV lesions in whom pregnancy is contraindicated, permanent contraception (tubal ligation or partner vasectomy) should be explicitly discussed. The conversation is difficult. It acknowledges that the condition limits reproductive autonomy. But failing to have this conversation leaves women facing fatal pregnancies that could have been prevented.

The Multidisciplinary Pregnancy Team

When a woman with CHD chooses to proceed with pregnancy, care must be centralized at a tertiary center with adult congenital heart disease expertise, maternal-fetal medicine, cardiac anesthesia, and high-risk obstetric nursing.

The evidence base for this recommendation is clear. The ROPAC (Registry of Pregnancy and Cardiac Disease) data demonstrate that outcomes improve with expert center care. Mortality is higher when women with complex CHD deliver at hospitals without appropriate expertise.

Care coordination includes:

• Monthly cardiology visits through the second trimester, then every two weeks
• Serial echocardiography monitoring ventricular function
• Rhythm surveillance with patient-activated monitors
• Delivery planning including mode, timing, and hemodynamic monitoring
• Anesthesia consultation for labor analgesia and cesarean section backup
• Anticoagulation bridging protocols for mechanical valves

Vaginal delivery is preferred for most women with CHD. Cesarean section does not protect the heart; it increases blood loss and fluid shifts. Cesarean is reserved for obstetric indications or specific lesions (severe aortic dilation, acute heart failure, need for concurrent cardiac surgery).

The third stage of labor and immediate postpartum period carry the highest hemodynamic risk. Autotransfusion of 300 to 500 mL of blood from the contracting uterus increases preload abruptly. For women with fixed cardiac output (Fontan) or limited preload reserve (pulmonary hypertension), this moment can precipitate acute decompensation. Invasive hemodynamic monitoring with arterial lines and sometimes pulmonary artery catheters is appropriate for high-risk deliveries. 4 / Promising

What You Can Do Now

If you have congenital heart disease and are considering pregnancy, your next step is not a home pregnancy test. Your next step is a formal preconception evaluation.

At your next cardiology appointment, ask for these specific elements by name: echocardiography with Doppler assessment of all valves and ventricular function, exercise stress test with oxygen consumption measurement, rhythm monitoring, and calculation of your CARPREG II score and mWHO classification. Request a medication review for teratogenicity. If your cardiologist does not have adult congenital heart disease expertise, ask for referral to an ACHD center.

If you have been told pregnancy is contraindicated, request a consultation specifically to discuss contraceptive options that account for your cardiac physiology. If you are already pregnant and have CHD, contact a tertiary center with a pregnancy heart team immediately, regardless of how simple your lesion was described in childhood.

Print this article. Bring it to your appointment. The conversation that begins with “repaired is not the same as normal” may be the conversation that saves your life.

Frequently Asked Questions

Is pregnancy safe after congenital heart defect repair?

Repair reduces risk but does not eliminate it. The CARPREG II study demonstrated that even women with “repaired” CHD face measurable pregnancy risks depending on the specific lesion, quality of repair, residual hemodynamic abnormalities, and current functional capacity. A woman with repaired tetralogy of Fallot who has good ventricular function and no significant pulmonary regurgitation may have a CARPREG II score of 0, predicting 2.9% risk of maternal cardiac events. The same lesion with severe pulmonary regurgitation, right ventricular dilation, and functional limitation might score 3 or higher, predicting over 22% risk. Every repaired lesion requires individual risk assessment by an adult congenital heart disease specialist before pregnancy is attempted.

What is the CARPREG II score and why does it matter?

CARPREG II is a validated risk prediction tool developed from 1,938 pregnancies in women with heart disease. It assigns points based on ten predictors including prior cardiac events, functional class, ventricular function, valve disease, mechanical valves, aortopathy, pulmonary hypertension, coronary disease, high-risk lesions, and late pregnancy assessment. The total score predicts probability of primary maternal cardiac events (heart failure, arrhythmia, stroke, or death) during pregnancy. A score of 0 predicts 2.9% risk. A score of 1 predicts 7.5% risk. A score of 4 or higher predicts 41% risk. This quantification allows informed decision-making and identifies modifiable factors, particularly the importance of early preconception evaluation.

Which congenital heart defects make pregnancy most dangerous?

The highest-risk lesions are classified as mWHO Class IV, meaning pregnancy is contraindicated due to extremely high maternal mortality. Eisenmenger syndrome carries 30 to 50 percent maternal mortality because fixed pulmonary hypertension cannot accommodate the cardiac output demands of pregnancy, leading to right heart failure and sudden death. Severe pulmonary arterial hypertension from any cause carries similar risk. Severe systemic ventricular dysfunction (ejection fraction below 30%), severe symptomatic aortic stenosis, and severe native coarctation also represent contraindications. Fontan circulation and mechanical heart valves are mWHO Class III, meaning pregnancy is possible but carries significantly increased risk requiring expert center care.

Can women with Fontan circulation have safe pregnancies?

Pregnancy in Fontan circulation is possible but carries substantial risk. The systematic review by van Hagen and colleagues found 44% of women with Fontan circulation experienced maternal cardiac events during pregnancy, predominantly arrhythmias (22%) and heart failure (15%). The Fontan circulation lacks a subpulmonary ventricle, making pulmonary blood flow entirely dependent on passive venous pressure. Pregnancy-induced venodilation reduces venous return. Uterine compression of the inferior vena cava further compromises preload. Live birth rates are 60 to 70 percent, with high rates of prematurity. These pregnancies absolutely require management at tertiary centers with adult congenital cardiologists, maternal-fetal medicine specialists, and cardiac anesthesiologists experienced in Fontan physiology.

What tests should I have before getting pregnant with CHD?

The preconception evaluation should include echocardiography assessing ventricular function, valve function, and residual lesions. For women with aortopathy or history of aortic surgery, CT or MRI should measure aortic dimensions. Cardiopulmonary exercise testing measures peak oxygen consumption and ventilatory efficiency, which predict pregnancy tolerance. A VO2 max below 16 mL/kg/min predicts adverse outcomes. Holter monitoring or extended rhythm surveillance identifies arrhythmia substrate. All current medications must be reviewed for teratogenicity, as ACE inhibitors, ARBs, amiodarone, warfarin, and statins all require discontinuation or substitution before conception. Your cardiologist should formally calculate your CARPREG II score and mWHO classification and document these in your medical record.