Abstract 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 Keywords Adult congenital heart disease; Pregnancy; Obstetric; Cardiology 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