Pregnancy and Congenital Heart Disease

Impact of Pregnancy on the Cardiovascular System

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.

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.

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 ).

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