As outlined above, one of the highest risk conditions is the Eisenmenger syndrome whereby a left to right shunt caused by a congenital heart defect causes increased flow through the pulmonary vasculature, causing pulmonary hypertension, which in turn causes increased pressures in the right side of the heart and reversal of the shunt into a right-to-left shunt. This is high risk from the combination of pulmonary hypertension and systemic cyanosis from the resultant right to left shunting. Pulmonary hypertension is generally considered to be elevated pulmonary arterial pressures (with varying cut-offs for mean pulmonary artery pressures) with impairment of right ventricular function. Potential consequences of pulmonary hypertension in pregnant and postpartum women include pulmonary hypertensive crises, pulmonary thrombosis, and refractory right heart failure [17]. Additional risks of the Eisenmenger syndrome that can be attributed to cyanosis include heart failure, supraventricular tachycardia, infective endocarditis, and thromboembolism. The risk for thromboembolism must be balanced with concurrent risk for hemoptysis and thrombocytopenia [17]. Maternal mortality in the Eisenmenger syndrome varies from 28 to 36 %, with the time period of highest risk being the month following delivery [23, 24]. Risk is increased with late presentation to the hospital, more severe pulmonary hypertension, and requirement of delivery under general anesthesia [24]. Given the significant maternal risk, women with the Eisenmenger syndrome or pulmonary hypertension should be counseled to avoid pregnancy. It is important to note that some pulmonary hypertension medications like bosentan decrease the efficacy of hormonal contraception [25]. The fetus is at risk for premature delivery or demise in the presence of maternal cyanosis, with <12 % chance of live birth with maternal oxygen saturation <85 % or polycythemia to hemoglobin of >20 g/dL preceding pregnancy [17, 26]. Management includes continuation of pulmonary hypertensive medications, possible bedrest, consideration of prophylaxis of thromboembolism, judicious use of diuretics to avoid volume depletion, treatment of iron deficiency, and frequent monitoring of oxygen saturation and complete blood counts. During delivery, regional anesthesia is preferable to general, and early cesarean delivery may become necessary if maternal or fetal deterioration is evident [17].

Severe coarctation of the aorta is also a high risk lesion. It poses a significant risk for hypertensive disease to the mother, which can result in rupture to aortic or cerebral aneurysms [17]. In one series, risk for maternal mortality during pregnancy was 2 % [27]. Good control of blood pressure is critical, though this must be balanced by avoiding placental hypoperfusion with overly aggressive blood pressure control. Percutaneous intervention for coarctation is possible during pregnancy, though the risk dissection with the procedure is higher during pregnancy. Thus, this is typically only attempted in the peripartum period when medical management has failed and there is clear evidence of fetal or maternal compromise [17].

The major risk for Marfan syndrome with aortopathy is aortic dissection during pregnancy, and patients with higher degree of aortic dilatation are considered WHO pregnancy class IV. As in non-pregnant patients, risk for dissection correlates directly with aortic root diameter, with the largest risk occurring in patients with aortic diameter >40 mm. It is thought that historically, the risk for dissection was over-estimated due to case reports with potential biases. Now, studies have demonstrated that pregnancy apparently has little effect on aortic dilatation in Marfan syndrome [28]. Complications of dissection include worsening mitral regurgitation, supraventricular arrhythmias, heart failure, and acute blood loss. Since pregnant women and the fetus have decreased ability to tolerate these complications, Marfan patients at greatest risk for dissection with aortic root diameter >45 mm should be counseled that pregnancy is contraindicated. Monitoring includes echocardiography every 1–3 months during pregnancy and again 6 months postnatally [17]. Medical management typically includes beta blockade due to potential for protection from more rapid aortic dilatation, though there is limited data confirming this effect [29]. Fetal growth must be monitored with mothers on beta blockers, with greater risk for fetal growth impairment with atenolol [17]. Both vaginal and cesarean delivery may be considered, with the primary goal of minimizing the cardiovascular stress of delivery as much as possible through continuation of beta blockade and expedition of some stages of labor and delivery [17] (Table 14.6).

Mitral stenosis (MS) due to rheumatic heart disease is the most common valvular anomaly that becomes clinically significant in pregnancy, and if severe (with valve area <1.0 cm²), is a contraindication to pregnancy [17, 30]. Women should be counseled that their symptoms will worsen during pregnancy. The increase in heart rate and stroke volume during pregnancy increases the pressure gradient across the narrowed mitral valve. This leads to further increase in left atrial volume and pressure with subsequent pulmonary congestion, worsening dyspnea, orthopnea, reduced exercise tolerance, and potentially atrial fibrillation [17, 31]. Maternal mortality is reported between 1 and 3 % [17]. Requirement for hospitalization was uniform in one series of women with severe mitral stenosis, and 15 % required surgical repair during pregnancy [32]. Fetal risks include prematurity, intrauterine growth retardation, and fetal or neonatal demise (up to 3 %) [31]. Both severity of mitral stenosis and resulting heart failure symptoms are directly correlated with maternal and fetal complications. Maternal complications include worsening heart failure, need for surgery or balloon valvuloplasty, thromboebmolism, and death. Fetal complications include premature birth, small for gestational age, respiratory distress, and death [33, 34]. Ideally, severe mitral stenosis would be repaired prior to pregnancy, which can decrease pregnancy risk from WHO class IV to class II or III [20]. During pregnancy, echocardiograms should be performed monthly, or sooner if symptoms warrant. The goal of medical management of mitral stenosis during pregnancy is to decrease heart rate and minimize left atrial enlargement [35]. If symptomatic pulmonary hypertension develops, women should have their activity restricted and they should be started on a selective beta 1 antagonists. Selective beta 1 antagonists are preferred due to the role of beta 2 receptors in uterine relaxation. Metoprolol is preferred over atenolol due to the potential for greater fetal growth restriction with atenolol [17]. Fluid status should be monitored closely and managed with fluid restriction or gently diuresis, avoiding hypotension and potentially catastrophic placental hypoperfusion [35]. Women with mitral stenosis during pregnancy are at increased risk for atrial arrhythmias, and management of these will be addressed in the following section on acquired heart disease during pregnancy. Percutaneous mitral valve balloon valvotomy may be considered after 20 weeks gestation in women with significant heart failure symptoms (NYHA Class III or IV) who have failed medical management [35]. Delivery should be vaginal in women without pulmonary hypertension and NYHA class I or II heart failure symptoms, while cesarean delivery is favored in women with NYHA class III or IV heart failure symptoms and pulmonary hypertension [17].

Severe aortic stenosis places women at very high risk for complications during pregnancy. The most common cause of aortic stenosis in women of childbearing age is congenital bicuspid aortic valve [17]. Symptomatic severe aortic stenosis is defined as a valve area ≤1 cm² or peak gradient ≥64 mmHg in the presence of dyspnea on exertion, chest pain, or syncope, or an abnormal exercise stress test. The risk for maternal mortality was previously thought to be as high as 17 % [36]. More recent series show that maternal mortality is rare [37]. Symptoms of aortic stenosis, including angina, dyspnea, and syncope, typically worsen or even appear for the first time during pregnancy. In all grades of aortic stenosis, increased cardiac output during pregnancy leads to increases in transvalvular aortic gradients [32]. 10 % of patients with severe aortic stenosis experience signs and symptoms of heart failure during pregnancy, and anywhere between 3 and 25 % will develop arrhythmias [38]. Such complications are rare in mild or moderate disease [37]. Women with aortic stenosis should be monitored carefully during pregnancy with monthly or bimonthly echocardiograms [17]. If signs or symptoms of heart failure develop, patients should be managed with activity restriction, gentle diuresis, and treatment of arrhythmias. Percutaneous valvuloplasty may be attempted during pregnancy in patients without evidence of calcification or aortic regurgitation [39]. Delivery in severe symptomatic aortic stenosis should be by cesarean section with general anesthesia, and in some cases early cesarean delivery with subsequent surgical aortic valve replacement is required [17].

Pulmonary hypertension from an acquired causes such as lung disease, hypoxia, and chronic thrombo-embolic disease is managed the same as pulmonary hypertension from congenital heart disease, which was addressed previously. A mean PAP ≥25 mmHg at rest is indicative of pulmonary hypertension. The risk probably increases with more elevated pulmonary pressures.

Patients with transposition of the great arteries generally fall into WHO class III for pregnancy risk. Whether corrected in utero (known as congenitally corrected transposition of the great arteries or atrioventricular and ventriculo-arterial discordance), or surgically after birth with an arterial switch operation (Senning or Mustard repair), risk is apparently similar [17]. Pregnancy complications include potentially life-threatening arrhythmias, hypertensive disease, worsening heart failure symptoms, and irreversible decline in right ventricular function [17, 40]. Patients with transposition of the great arteries are at increased risk for AV nodal blockade and bradycardia, so beta blockers must be used with caution. Cardiac follow up should occur frequently during pregnancy, with echocardiograms and ECGs every 1–2 months. Vaginal delivery is usually appropriate in the absence of any hemodynamic decompensation [17].

Pregnancy risk for women with who have had the Fontan procedure depends on the hemodynamics of the circuit, with better prognosis and lower risk in women with a more optimal circuit [17]. Maternal complications include atrial arrhythmias and worsening heart failure symptoms, and there is increased risk for fetal loss, premature birth, and small for gestational age size [41]. Patients should be evaluated by a cardiologist monthly during and immediately following pregnancy. ACE inhibitors must be discontinued, and anticoagulation to prevent thrombo-embolism should be considered. Vaginal delivery is preferred, though early cesarean delivery may be necessary if worsening heart failure occurs [17].

Mechanical valves are WHO class III. In women of child-bearing age, mechanical valves have the advantage of excellent hemodynamics and higher durability when compared with bioprosthetic valves. The major disadvantage is the risk for valve thrombosis, which can be fatal, and the potential complications of full anticoagulation during pregnancy. The risk for teratogenicity on warfarin is 6.4 %. Warfarin crosses the placenta and typically causes primarily central nervous system abnormalities. The risk for warfarin embryopathy can be effectively eliminated with substitution of heparin beginning by 6 weeks gestation through 12 weeks, and then resumption of oral anticoagulation with warfarin until delivery is planned [42]. Women requiring lower warfarin doses (<5 mg per day) have a 2.6 % risk of teratogenesis while women on higher doses (>5 mg per day) have an 8 % risk [43]. However, the risk for valve thrombosis is directly related to the time spent on heparin in place of warfarin, with 3.9 % thrombosis with only oral anticoagulation, 9.2 % for heparin in the first trimester, and 33 % for heparin throughout pregnancy [42]. These risks must be weighed by the patient and physician, and will inform the decision regarding anticoagulation regimen. Close monitoring of anticoagulation and evidence of possible valve thrombosis should be performed throughout pregnancy. Vaginal delivery is contraindicated for pregnant women on warfarin due to the risk for neonatal intracranial hemorrhage. Given the concurrent risk for maternal hemorrhage with cesarean section on warfarin, planned vaginal delivery with transition back to heparin is preferred [17].