The successes of pediatric cardiology and cardiac surgery have enabled a new cohort of women, born with congenitally malformed hearts, to reach adulthood. Many of these women are now considering pregnancy. Most women in this new cohort can anticipate safe and successful pregnancies. Pregnancy, however, imparts an additional hemodynamic load, is prothrombotic, and increases the propensity to arrhythmias, all of which increase the risk of adverse maternal cardiac events. In addition, women with heart disease are at higher risk for fetal and neonatal complications. Recognition and appropriate management of such risks, when present, should optimize outcomes, whereas the identification of women with congenitally malformed hearts who are at low risk allows for welcome reassurance.
Impact of Pregnancy on the Cardiovascular System
Hemodynamic Changes During Pregnancy
Many physiologic changes occur during pregnancy. The maternal blood volume increases by approximately 50%, beginning during the first trimester and peaking in the third trimester. The average heart rate increases by 10 to 20 beats/min. Beginning early in the first trimester, the systemic vascular resistance and systemic arterial pressure begin to decrease owing to the low-resistance circuit in the uterus and to the effects of endogenous vasodilators. The systemic vascular resistance decreases until midpregnancy, plateaus, and then by the end of pregnancy rises toward the levels existing prior to pregnancy. Systemic arterial pressure also begins to return toward prepregnancy levels in the third trimester. The changes in blood volume, vascular resistance, and heart rate all contribute to an increase in cardiac output, which begins early in the first trimester, continues to increase until approximately the end of the second trimester, rising to levels between 30% and 50% higher than the levels existing prior to pregnancy, and then plateaus until term. Cardiac output is affected by position, being highest when the mother is lying on her left side. The supine gravid uterus can compress the inferior caval vein, which limits venous return and may result in a substantial reduction in cardiac output.
Labor is associated with a further increase of approximately 10% in basal cardiac output, augmented by an additional surge with each uterine contraction. Anxiety, pain, tachycardia, and hypertension or hypotension also contribute to cardiac complications at the time of labor and delivery. Following delivery, there is a further increase in cardiac output due to relief of compression on the inferior caval vein and autotransfusion from the now fully contracted uterus. Rapid mobilization of interstitial fluid in the immediate period following pregnancy may have a significant negative impact on a woman with already compromised cardiac function. Although many of the described changes regress within the first few days after delivery, complete resolution of pregnancy-induced effects on cardiac function may not occur until 6 months after delivery.
Cardiac Symptoms and Signs in Normal Pregnancy
During pregnancy women often experience fatigue, dyspnea, tachypnea, palpitations, presyncope, and decreased exercise tolerance. Such symptoms can be identical to those of cardiac decompensation, and clinicians must be careful to differentiate this possibility. Blood pressure decreases during the first part of pregnancy and then, during the last 6 weeks, reaches or exceeds prepregnancy levels. Blood pressure should be taken when the mother is sitting or lying on her left side to avoid a falsely low reading caused by supine caval venous compression, limiting venous return. The diastolic blood pressure falls more than the systolic pressure, resulting in a wide pulse pressure. The heart rate increases. Peripheral edema may be noted. There may be a laterally displaced apical impulse due to modest increase in cardiac size, as well as upward displacement of the heart by the gravid uterus. There is often prominence of the jugular venous pulsation. There may be wide splitting of the first and second heart sounds. A systolic flow murmur is common, secondary to the hyperdynamic circulation, and is best heard at the left lower sternal border. The continuous murmur of a venous hum in the right supraclavicular fossa or a mammary souffle over an engorged breast can become apparent.
Impact of Pregnancy on Common Cardiac Diagnostic Tests
The surface electrocardiogram may show a sinus tachycardia. Because of the change in position of the heart, the electrocardiogram may show a shift in the frontal plane axis or inversion of the T waves in the inferior leads. The chest radiograph may show a more horizontal cardiac shadow because of elevation of the diaphragm and an enlarged cardiac silhouette. The pulmonary vascular markings may become more prominent due to increased blood flow, simulating the vascularity produced by a systemic-to-pulmonary shunt. Echocardiographically, the increase in blood volume manifests as mild increases in the dimensions of the atria and ventricles. The left ventricular mass increases. In normal pregnancies, the left ventricular systolic function is preserved. The increased cardiac output is associated with an increase in velocity of flow across all cardiac valves. Mitral regurgitation may either improve or worsen, depending on the relative impact of the fall in systemic vascular resistance versus the change in geometry of the mitral valvar apparatus associated with increasing chamber size.
Preconception Counseling and Contraception
All women with congenital heart disease should have age-appropriate counseling regarding contraception and potential pregnancy beginning in adolescence. The responsibility of providing such counseling often falls to the specialist in congenital cardiac disease caring for the woman at the time and his or her team, as the patient will often not have access to others qualified to offer knowledgeable advice. Table 80.1 lists issues that should be addressed during preconception counseling.
| Component | Description |
|---|---|
| Contraception selection | Review safety and reliability of contraception options |
| Maternal cardiac risk | Cardiac risk stratification by an expert in pregnancy and heart disease Determine if cardiac interventions are required prior to pregnancy Discuss cardiac risks of pregnancy Review medications and discontinue or modify as appropriate Discuss long-term prognosis |
| Maternal obstetric risk | Discuss maternal obstetric risks |
| Fetal and neonatal risk | Discuss fetal and neonatal risks Discuss risk of transmission of congenital heart disease to offspring Genetics referral when appropriate |
| Pregnancy planning | Discuss general pregnancy care planning including antenatal follow-up and delivery location |
Commonly, information regarding diagnosis, previous procedures, and prognosis are not known to patients or are misunderstood by them. Clarification of diagnosis and functional capacity are fundamental to effective preconception counseling. The specialist in congenital cardiac disease is well suited to this task and also to ensuring that this information is provided to other caregivers involved in the management of the pregnancy and understood by them. Discussion of long-term prognosis of the mother may be straightforward or very complex and sensitive, depending on the underlying cardiac lesion, the types of surgical interventions, the residual lesions, and comorbid medical conditions. Because maternal cardiac status can change over time, women with congenitally malformed hearts should be advised to ensure regular follow-up and, in particular, to obtain a contemporaneous updated assessment prior to finalizing a decision to pursue pregnancy. We discuss maternal and fetal risks associated with pregnancy in the later sections of this chapter.
When pregnancy is actively considered or when the woman presents in a gravid condition, the assessment must incorporate advice about the proper level of obstetric and multidisciplinary care during pregnancy. Most women with congenital heart disease will benefit from an initial cardiac and high-risk obstetric (maternal fetal medicine) consultation. Those with minor lesions and their caregivers and families can be reassured regarding the low risk of adverse events and the appropriateness of standard obstetric care. Women at higher risk can be referred appropriately to high-risk obstetric units in order to have access to specialists with experience in managing complex cardiac disease throughout pregnancy.
For women who do not wish to become pregnant, the safety and efficacy of various types of contraception must be considered. Recommendations regarding proper use of contraceptives have been extrapolated from studies in women without cardiac disease and are based on expert opinion. Barrier methods do not pose a health risk to the mother but are associated with high rates of failure. Up to one-third of women using barrier techniques alone will have an unintended pregnancy within the first year of use. Barrier methods alone, therefore, should not be recommended as effective contraceptive choices to women in whom there is a significant maternal risk of pregnancy, although condoms may be used in conjunction with other methods. Combined estrogen and progestin oral contraceptives have good efficacy, but the estrogen component is associated with an increased risk of thrombosis, which constrains their use in women with cyanotic cardiac disease, Fontan circulation, significant systemic ventricular dysfunction, sustained arrhythmias, mechanical valves, and/or prior thromboembolic events. The risk of stroke in association with combined oral contraceptives is further increased if a woman has a history of hypertension, diabetes, obesity, smoking, or migraine headaches. Estrogens and progestins can interfere with the metabolism of warfarin, and international normalized ratios need to be monitored more closely in women using these forms of contraception. Progestin-only oral contraceptives are safe in women with heart disease but are associated with higher rates of failure compared with combined oral contraceptives and should not be used in women with cardiac disease who face substantial risk of pregnancy. Insertion of an intrauterine device is often a safe and reliable option for women with heart disease. In some women, a vasovagal reaction will occur when the cervix is instrumented for placement of a device. This can be particularly hazardous in women with pulmonary hypertension and those with the Fontan circulation. Women in whom pregnancy carries a very high risk should consider sterilization. Vasectomy is sometimes a good alternative, but the possibility that the healthy male partner may outlive his spouse and wish to father children with a new partner should be considered. Emergency contraception (“the morning-after pill”) is available in forms containing estrogen and progestin, or progestin only, and is safe for women with congenital heart disease.
General Approach to Risk Assessment
Maternal cardiac disease is a risk factor for maternal, fetal, and neonatal complications during pregnancy, and careful risk stratification is an important aspect of care of the pregnant patient with heart disease. When pregnant women with cardiac disease are being evaluated, an assessment is made of the risk of adverse maternal cardiac events, with fetal and neonatal risks considered separately. Cardiac morbidity and mortality in pregnant women with heart disease in three of the large cohort studies are shown in Fig. 80.1 . The risk of pregnancy varies according to many factors, which are discussed in detail in the following text.
To estimate the maternal cardiac risk in pregnancy, general predictors of risk (e.g., maternal function class or the presence of cyanosis) should be integrated with lesion-specific risks (e.g., specific risks in women with the Mustard operation) and individual clinical variables. In 2001, a Canadian consortium (Canadian Pregnancy and Heart Disease Study: CARPREG Study) prospectively developed and validated the first general risk index for predicting risk in pregnant women with heart disease. The CARPREG risk score has subsequently been revised and the CARPREG II risk index includes 10 risk predictors: five general predictors (prior cardiac events or arrhythmias, poor functional class or cyanosis, high-risk valve disease/left ventricular outflow tract obstruction, systemic ventricular dysfunction, no prior cardiac interventions); four lesion specific predictors (mechanical valves, high-risk aortopathies, pulmonary hypertension, coronary artery disease); and one delivery-of-care predictor (late pregnancy assessment) ( Fig. 80.2 ). In addition to the CARPREG studies, other groups have developed risk prediction models ; Box 80.1 shows the reported predictors of adverse cardiac outcomes during pregnancy.
Cardiac events before pregnancy
Cardiac medications before pregnancy
Smoking history
New York Heart Association functional class III or IV
Cyanosis or oxygen saturation <90%
Systemic ventricular systolic dysfunction
Subpulmonary ventricular systolic dysfunction
Left heart obstruction
Pulmonary atrioventricular valve regurgitation
Systemic atrioventricular valve regurgitation
Mechanical prosthesis
Elevated brain natriuretic peptide levels
A British working group created a consensus-based classification of risk for women with cardiac conditions undergoing pregnancy that categorizes the risk using the World Health Organization (WHO) classification and primarily lesion-specific elements. The original classification has been modified and subsequently been shown to be a predictor of cardiac complications in women with heart disease. High-risk lesions according to the WHO classification are shown in Table 80.2 . Pregnancy is contraindicated in women with cardiac lesions associated with extremely high risk of maternal morbidity and mortality, including severe systemic ventricular dysfunction (systolic function <30%), peripartum cardiomyopathy with any residual left ventricular dysfunction, severe mitral stenosis, severe symptomatic aortic stenosis, Marfan syndrome with an aortic root diameter greater than 45 mm, and pulmonary arterial hypertension from any cause including Eisenmenger syndrome. Other factors that increase maternal cardiac risk during pregnancy include comorbid medical conditions such as diabetes and hypertension as well as the use of fertility therapy. Although the risks of adverse maternal events during pregnancy and the early peripartal period are reasonably well described, few data are available concerning late maternal outcomes in women with congenitally malformed hearts. In general, women who develop complications during pregnancy are at higher risk of complications late after pregnancy ( Fig. 80.3 ).
| WHO Risk Class | Risk of Pregnancy | Examples |
|---|---|---|
| III | Significant increase in the risk of maternal mortality or severe morbidity. Expert counseling required. If pregnancy is decided upon, intensive specialist cardiac and obstetric monitoring needed throughout pregnancy, childbirth, and the puerperium. | Mechanical valve |
| Systemic right ventricle | ||
| Fontan circulation | ||
| Cyanotic heart disease (unrepaired) | ||
| Other complex congenital heart disease | ||
| Marfan syndrome without aortic dilation Aorta dilation 40–45 mm in Marfan syndrome Aortic dilation 45–50 mm in aortic disease associated with bicuspid aortic valve | ||
| IV | Extremely high risk of maternal mortality or severe morbidity; pregnancy contraindicated. If pregnancy occurs, termination should be discussed. If pregnancy continues, care as for class III. | Pulmonary arterial hypertension of any cause |
| Severe systemic ventricular dysfunction (LVEF <30%, NYHA III or IV) | ||
| Previous peripartum cardiomyopathy with any residual impairment of left ventricular function | ||
| Severe mitral stenosis, severe symptomatic aortic stenosis | ||
| Marfan syndrome with aorta dilated >45 mm Aortic dilatation >50 mm in aortic disease associated with bicuspid aortic valve | ||
| Native severe coarctation |
Women with cardiac disease also have an increased risk of adverse fetal and neonatal events including premature birth, weight at birth small for gestational age, respiratory distress syndrome, intraventricular hemorrhage, and fetal or neonatal death. This risk is amplified by specific maternal cardiac risk factors and further amplified by concomitant maternal noncardiac risk factors for adverse fetal and neonatal outcomes. Fetal risks are inversely related to maternal cardiac output. There is also an increased risk of transmission of heart disease to offspring. Baseline probability of a congenitally malformed heart in the absence of an affected relative is from 0.4% to 0.6% but increases about 10-fold when a parent is affected, with some studies suggesting a higher rate of transmission when the mother is the affected parent. With some lesions the likelihood of transmission is higher. In autosomal dominant syndromes—such as the Noonan, Holt-Oram, Williams, and Marfan syndromes and the 22q11 deletion syndrome—the risk is 50%, though penetration and phenotypic expression may vary.
Specific Cardiac Lesions
Left-to-Right Shunts
Simple left-to-right shunts—including those produced by an interatrial communication, ventricular septal defect, and patency of the arterial duct—are generally well tolerated during pregnancy. The increase in volume load is counteracted to some extent by the fall in peripheral vascular resistance. Complications that have been described include arrhythmias, cardiac failure, and paradoxical embolism. However, these are rare; in a literature review, arrhythmias were reported in only 1 of 123 pregnancies in women with atrial septal defects and in no pregnancies in women with ventricular septal defects. No heart failure was reported in either group.
Atrioventricular septal defects are more complex and can be associated with regurgitation across both the right and left sides of the common atrioventricular junction. Compared with women with simple shunt lesions, those with atrioventricular septal defect are more likely to experience cardiac complications. When intracardiac shunts are associated with pulmonary hypertension, the risk is higher and mainly attributable to the pulmonary hypertension, discussed separately further on.
Aortic Stenosis and Other Left Ventricular Outflow Tract Lesions
A bicuspid aortic valve is the most common cause of an obstructed left ventricular outflow tract in women of childbearing age. A smaller number of cases are secondary to subvalvar or supravalvar stenosis or other abnormalities at the valvar level. Severe obstruction may not be well tolerated during pregnancy because the increased stroke volume may provoke left ventricular failure. Furthermore, the pressure-loaded, marginally compensated, hypertrophied ventricle may poorly tolerate loss of preload or depression of function, so hemorrhage or the effects of general or regional anesthetic agents can lead to hemodynamic embarrassment. During pregnancy, women with severe obstruction are at risk for angina, functional deterioration, cardiac failure, and arrhythmias as well as sudden death, although adverse maternal cardiac events are not as common as described in early reports. Maternal cardiac complications have been reported in approximately 5% or more of pregnancies. As many as two-fifths of patients with severe stenosis have required intervention within a few years after pregnancy, so this possibility should be addressed during prepregnancy counseling. Balloon aortic valvoplasty and aortic valvar surgery have been performed successfully during pregnancy. Because of the risk to the fetus, such interventions should be performed only if there are no other alternatives. Despite relatively reassuring maternal outcomes, fetal, neonatal, and obstetric complications are common in women with aortic stenosis. Women with moderate or severe aortic stenosis who have been pregnant have higher rates of late complications as compared with women with similar aortic stenosis who have not been pregnant. Aortic insufficiency, on the other hand, is generally well tolerated unless it is severe and associated with depressed left ventricular function.
Aortic Coarctation
Most women with coarctation of the aorta have had some type of repair. Repair may be associated with late sequelae, such as recoarctation, aneurysms at the repair site—especially when Dacron has been used for a patch—and pseudoaneurysms. Thus imaging of the site of repair, usually by magnetic resonance imaging, is optimal prior to conception. Patients with unrepaired coarctation or those with repaired coarctation and residual or recurrent obstruction are subject to upper body hypertension. Antihypertensive treatment directed at the upper body may exacerbate hypotension distal to the coarctation, and this theoretically could compromise placental perfusion. In contemporary studies, maternal mortality in women with repaired coarctation is rare, but women are at increased risk for pregnancy-induced hypertension, preeclampsia, and complications related to the associated bicuspid aortic valve. Dissection of the aorta has been reported.
Pulmonary Valvar Stenosis
Women with pulmonary valvar stenosis tolerate pregnancy well in spite of the pregnancy-associated increase in preload.
Tetralogy of Fallot
Most patients with tetralogy of Fallot will have undergone an intracardiac repair, and many will have pulmonary regurgitation and/or right heart dilation and dysfunction late after their repair. Other residua and sequelae include surgical scars and patches that can act as a substrate for arrhythmia, residual shunts, and left ventricular dysfunction. In general women with tetralogy of Fallot often do well in pregnancy, although arrhythmias and right-sided heart failure can occur. Women with severe pulmonary regurgitation and right ventricular (RV) dysfunction, RV hypertrophy, or branch pulmonary stenosis are at increased risk of developing right heart failure during pregnancy. In small series, RV dilation was increased in women who had been pregnant compared with women who had never been pregnant.
Ebstein Anomaly
Ebstein anomaly comprises a broad spectrum of severity. Those with severe forms of the disease may present early in life with cyanosis or right-sided cardiac failure, whereas those with mild forms may first be detected incidentally in adulthood. The ability of the heart to tolerate the increased demands of pregnancy is dependent on the size and function of the functional right ventricle, the degree of tricuspid regurgitation, and the propensity to arrhythmias. Women with interatrial communications (atrial septal defect or patent foramen ovale) are at risk for right-to-left shunting if they are unable to adapt to the increased preload, and women who enter pregnancy with an established right-to-left shunt at the atrial level are likely to demonstrate worsening hypoxemia and cyanosis as pregnancy proceeds. Despite these potential problems, reported pregnancy outcomes have been favorable.
Complete Transposition of the Great Arteries
Atrial switch procedures (Mustard or Senning operation) were the earlier techniques used to repair patients with transposition, albeit now these are superseded in most instances by the arterial switch operation. Most women with transposition now of childbearing age will have had an atrial repair in infancy; as a consequence they will have the morphologically right ventricle and tricuspid valve supporting the systemic circulation, which is associated with variable degrees of systemic ventricular dysfunction and systemic atrioventricular valvar regurgitation. Additional sequelae that may affect pregnancy include a propensity to atrial arrhythmias, sinus nodal dysfunction, and obstruction or leak across the atrial baffle. Cardiac failure, functional deterioration, and arrhythmias are the main complications reported during pregnancy. Late echocardiographic evidence of systemic ventricular dilation has been reported in almost one-third of such women, and deterioration in the function of the systemic ventricle in one-quarter. In addition, obstetric complications, such as premature rupture of membranes, premature labor, and premature delivery are frequent.
Although only limited outcome data are available for women with arterial switch operations who have more recently reached childbearing age, it is anticipated that women without major residua and sequelae after repair will do well.
Congenitally Corrected Transposition
Congenitally corrected transposition is also associated with a morphologically right ventricle supporting the systemic circulation. Frequently associated anomalies include regurgitation of the abnormal systemic atrioventricular valve, ventricular septal defect, pulmonary stenosis, and/or disturbances of atrioventricular conduction. Although maternal deaths have not been reported, cardiac failure, arrhythmias, endocarditis, stroke, and myocardial infarction (in the setting of a single coronary artery) have been described as complications of pregnancy.
Functionally Univentricular Hearts and the Fontan Circulation
The Fontan procedure, initially developed as a palliation to improve hemodynamics and relieve hypoxemia in patients with tricuspid atresia, has been extended to individuals with other complex congenital cardiac lesions not amenable to biventricular repair. Despite overall benefit, patients remain with functionally univentricular physiology and have limited ability to increase cardiac output. Late complications in patients with the Fontan circulation include elevated right atrial and systemic venous pressures, arrhythmias, ventricular dysfunction, protein-losing enteropathy, and thromboembolic complications. All these problems can be provoked or aggravated by the additional hemodynamic load of pregnancy. Women with the Fontan circulation must be educated about the potential maternal risks of pregnancy; if they choose to become pregnant, they must be monitored closely. Maternal arrhythmias, heart failure, and hemorrhagic/thrombotic and noncardiac complications are reported. Miscarriages are common and have been reported in half of those becoming pregnant.
Cyanotic Cardiac Disease
Cyanosis is the visible manifestation of maternal hypoxemia. In a woman with manifest or potential hypoxemia owing to right-to-left shunting, it should be established whether the shunt is due to pulmonary hypertension (often Eisenmenger syndrome) or another cause, since pulmonary hypertension itself imparts an extremely high risk to pregnancy, as discussed later. Even in the absence of pulmonary hypertension, women with cyanotic disease are at risk for adverse maternal cardiac events during pregnancy, in particular cardiac failure, arrhythmias, thrombosis, embolism, and endocarditis, although death is rare. The pregnancy-induced fall in systemic vascular resistance will facilitate right-to-left shunting, especially when the shunt is at the level of the ventricles or great arteries. Fetal outcomes are poor. Infants are born small for gestational age. Live births are compromised, and prematurity is common. If maternal saturation of oxygen is less than 85%, only one-eighth of fetuses progress to be born alive.
Pulmonary Hypertension
In spite of advances in treatment, pulmonary hypertension continues to impart a very high risk for pregnancy. The increased volume load directed through the high-resistance pulmonary circuit will provoke elevations in subpulmonary ventricular pressure, potentially causing subpulmonary ventricular failure, and will augment a right-to-left shunt if present, thereby worsening hypoxemia. Hypoxemia acts as a pulmonary vasoconstrictor, thus establishing a vicious cycle. In addition, pulmonary thrombosis and pulmonary embolus are more likely during pregnancy and may further increase pulmonary vascular resistance. Challenges at delivery—including loss of blood, epidural anesthesia, and adverse hemodynamic responses associated with expulsive efforts of the mother in the second stage of labor—may further facilitate right-to-left shunting, leading to a potential spiral of hypoxemic pulmonary vasoconstriction, hypotension, and death.
Overall, the high mortality of pregnancy in Eisenmenger syndrome has remained in the range of 30%. Outcomes may be better with early diagnosis and comprehensive management. Targeted advanced pulmonary vascular therapies applied in specialized centers are likely to provide better outcomes, although reports of such improved outcomes are limited and the risk remains high. As a consequence, the widely held consensus is to advise against pregnancy in women with significant pulmonary hypertension of any cause and, in the event of unexpected pregnancy, to offer termination as the safest option.
Marfan Syndrome and Other Aortopathies
Pregnancy-related hemodynamic and hormonal changes affect the structure of the aortic wall and increase the risk of dilation and dissection. This phenomenon manifests as an increased risk of spontaneous dissection even in women with no known or diagnosable aortopathy. Dissection risk is very low in otherwise normal women. Dissection has best been described in women with Marfan syndrome, but those with other aortopathies that have genetic and/or pathologic similarities—such as familial thoracic aortic aneurysm and dissection syndromes, Loeys-Dietz syndrome, the aortopathy associated with bicuspid aortic valve, Turner syndrome, and vascular Ehlers-Danlos syndrome—are also at increased risk of aortic complications.
In a prospective study of women with Marfan syndrome followed through 45 pregnancies, no significant change was found in the size of the aortic root in those initially exhibiting roots of normal size, but one-third of women with dilated roots or those having had prior aortic surgery experienced either aortic dissection or progressive aortic dilation. In a single-center study, favorable outcomes were reported in a large cohort of women carefully followed throughout pregnancy, although aortic growth rate increased during pregnancy and did not return to baseline after pregnancy. Although there are no trials demonstrating specific benefit during pregnancy of β-adrenergic–blocking drugs in women with aortopathy, many experts recommend such treatment during and after pregnancy in women with Marfan syndrome and other high-risk aortopathies in the hope that this may attenuate the risk of aortic dilation or dissection.
Prosthetic Heart Valves
Women with any type of artificial heart valve are at increased risk for complications during pregnancy. Bioprosthetic and mechanical valves each have advantages and disadvantages. Careful consideration of the risks and benefits of each is required prior to selection of the type of prosthetic valve in a woman of childbearing age. During pregnancy, normally functioning bioprosthetic valves are safer than mechanical valves because they are less thrombogenic and do not require ongoing anticoagulation. Bioprosthetic valves, nonetheless, have limited durability, and women with these valves will generally require repeated surgery in the future. Although some studies have suggested that pregnancy accelerates the degeneration of bioprosthetic valves, others have not supported this finding. Less information is available on the safety of homografts during pregnancy, although one study found no valve-related complications during pregnancy.
Mechanical valves have better durability than bioprosthetic ones but are associated with significantly greater maternal and fetal risks during pregnancy. Because pregnancy is a hypercoagulable state and anticoagulation can be difficult to manage with changing body weight during pregnancy, there is an increased risk of maternal thromboembolic events, of which approximately half are valvar thrombosis. Many factors influence the risk of valve thrombosis and poor outcomes in pregnancy. Valves in the mitral position carry higher thrombotic risks than those in the aortic position, as do early models of mechanical valves, such as those with balls in cages or the first generation of those with tilting discs. However, one of the most important determinants of thrombosis risk is the type of anticoagulation used during pregnancy, as discussed later. Anticoagulant therapy is complicated by risk of bleeding. Systematic reviews have reported on maternal and fetal risks in pregnant women with mechanical valves. Risks of maternal and fetal adverse outcomes in pregnant women with mechanical valves according to type of anticoagulant used in pregnancy are shown in Table 80.3 .
