Increases in blood volume, red cell mass, and heart rate result in a 50% antepartum increase in cardiac output.¹¹ Increases in left ventricular (LV) volume are present by 14 weeks gestation and reach maximum levels early in the third trimester but contractility remains in the normal range. Gestational hormones, circulating prostaglandins, and the low-resistance vascular bed in the placenta result in decreased peripheral vascular resistance and blood pressure. During labor and delivery, there are additional increases in cardiac output and oxygen consumption. Immediately following delivery, relief of caval compression and autotransfusion from the emptied uterus result in a transient increase in cardiac output. Most of the hemody-namic changes of pregnancy have resolved by the second postpartum week but complete return to baseline may not occur until six months after delivery.

Congenital heart lesions

Volume overload lesions

Left-to-right shunts

The effect of increased cardiac output on the volume-loaded right ventricle (RV) in atrial septal defect (ASD) or LV in ventricular septal defect (VSD) and patent ductus arteriosus (PDA) is counterbalanced by a decrease in peripheral vascular resistance during pregnancy. Therefore, pregnancy and delivery are well tolerated in the absence of pulmonary hypertension.^1,12–15 In a recent overview, significant arrhythmia requiring therapy was reported in 1/123 pregnancies with ASD (0.8%) and in no pregnancies with VSD; there were no reports of CHF.⁹ Paradoxic embolization may be encountered, albeit infrequently, if systemic vasodilation and/or elevation of pulmonary resistance promotes transient right-to-left shunting (particularly in the setting of an ASD).

Atrioventricular septal defect (AVSD), a more complex form of septal defect, may be less well tolerated in pregnancy as compared with simpler defects described above. A recent retrospective review of 48 pregnancies reported postpartum persistence of NYHA class deterioration, arrhythmias and worsening of pre-existing left atrioventricular valvular regurgitation in 23%, 19% and 17%, respectively.¹⁶

Regurgitant valves

Significant pulmonary regurgitation (PR) is commonly seen after tetralogy of Fallot (TOF) repair, particularly if a transannular patch was applied. Sequelae of severe PR include RV dilation and dysfunction. From a retrospective review of 82 successful pregnancies (including 20 pregnancies in women with unrepaired TOF), cardiovascular events occurred in six women (14%) and included supraventricular arrhythmia, CHF, pulmonary hypertension and pulmonary embolus. In 5/6 women, cardiovascular complications were associated with the following: severe PR with RV dilation, RV hypertension and peripartum LV dysfunction.¹⁷ Another study of 50 pregnancies in women with corrected TOF found cardiac complications in 12% of pregnancies, consisting of CHF, arrhythmia or both.¹⁸

Important congenital tricuspid valve insufficiency is commonly related to structural disease, such as Ebstein anomaly. Apical displacement of the tricuspid valve results in atrialization of the RV and commensurate compromise in functional RV size. A diminutive functional RV may not be able to accommodate the increased stroke volume of pregnancy, resulting in worsening tricuspid insufficiency, raised right atrial pressure and right-to-left shunting across the atrial septum. A study of 111 pregnancies in women with Ebstein anomaly did not find any serious maternal complications but did note increased risk of prematurity and fetal loss; birth weight was significantly lower in those born to cyanotic women.¹⁹

Both mitral and aortic regurgitation during pregnancy are generally well tolerated, even if severe, due to reduced antenatal systemic vascular resistance resulting in reduced afterload. Symptoms usually respond to medical therapy.^20,21

Pressure overload lesions: left heart

Left ventricular outflow tract obstruction

When aortic stenosis (AS) complicates pregnancy it is usually due to a bicuspid aortic valve (BAV), which may also be associated with aortic coarctation and/or ascending aortopathy. Subvalvular and supravalvular AS have similar hemodynamic consequences to valvular AS. Women with symptomatic AS should delay pregnancy until after surgical correction²⁰ (Class I, Level C2). Women with moderate or severe AS continue to be at increased risk for pulmonary edema or arrhythmia during pregnancy, even if they are asymptomatic prior to conception.^1,12,22,23 Contemporary studies report either no or low maternal mortality despite including a significant number of women with severe AS.^23–25 Antenatal percutaneous balloon valvuloplasty for symptomatic AS is preferable to cardiac surgery which carries substantial fetal mortality (Class I, Level C1).^22,26–29 In the absence of prosthetic valve dysfunction or residual AS, those with a tissue prosthesis usually tolerate pregnancy well. Pregnancy has not been clearly shown to accelerate degeneration of bioprosthetic or homograft valves.^30,31 In two reports, 24 completed pregnancies in women post Ross operation (pulmonary autograft aortic valve replacement) were described and no cardiac complications were reported during pregnancy; one woman developed a dilated cardiomyopathy six months after delivery unrelated to aortic valve dysfunction.^32,33

Pregnancy in a woman with a mechanical valve prosthesis carries increased risk of valve thrombosis as a result of the prothombotic state of pregnancy. Thrombosis risk during pregnancy is also influenced by valve type (more likely in older-generation valves), position (greater in the mitral as compared with the aortic position), prenatal level of valve function, and type of anticoagulation used.³⁴

Coarctation of the aorta

In 308 pregnancies reported in four contemporary studies, the only maternal death occurred as a result of dissection in a woman with Turner syndrome who had previously undergone coarctation repair.^1,12,35,36 In uncorrected coarctation, satisfactory control of upper body hypertension may lead to excessive hypotension below the coarctation site, compromising the fetus. Intrauterine growth restriction and premature labor are more common. Following coarctation repair, the risk of dissection and rupture is reduced but not eliminated.^35,37 Medical therapy with beta-blockade may reduce aortic wall stress but its clinical efficacy has not been formally studied in pregnancy. Pregnant women with repaired coarctation are at increased risk for pregnancy-induced hypertension, likely as a result of abnormal aortic compliance.^1,12,35

Aortopathies

Life-threatening aortic complications of Marfan syndrome are primarily due to aortic dissection resulting from medial aortopathy which often manifests as aortic dilation. Risk is increased in pregnancy due to hemo-dynamic stress and perhaps hormonal effects. A prospective study of 45 pregnancies in 21 patients reported no increase in obstetric complications or significant change in aortic root size in patients with normal aortic roots. Importantly, in the eight patients with a dilated aortic root (>40 mm) or prior aortic root surgery, 3/9 pregnancies were complicated by aortic dissection in two and rapid aortic dilation in one. Of note, beta-blockade therapy was withheld during pregnancy in the majority of women in this study.³⁸ A later prospective study of 33 pregnancies in 23 women with Marfan syndrome reported favorable outcomes with aortic root diameter <45mm and no previous history of dissection. There was a small but statistically significant increase in aortic root diameter during pregnancy in women with an initial diameter >40mm as compared with those <40mm.³⁹ Surgical repair should be offered to women prior to conception if the aortic root diameter is >40–45mm,²⁰ though this is unlikely to normalize the risk of dissection thereafter.⁴⁰ Thus, patients with aortic root involvement should receive preconception counseling emphasizing their risk, and in early pregnancy should be offered termination (Class 1, Level C1) In contrast, women with normal aortic root diameter may tolerate pregnancy well, though there remains a possibility of dissection even with normal aortic dimensions. Serial echocardiography should be used to identify progressive aortic root dilation during pregnancy and for six months post partum.⁴¹ Despite the absence of trials specifically evaluating beta-blocker therapy in pregnancy, the potential benefit likely outweighs the relatively small risk of use of this medication during pregnancy (Class 1, Level C2).

Less is known about risk factors for dissection in pregnant women with a dilated aorta in the context of a BAV, although this complication has been reported in the pregnant population.⁴² The histologic features of aortopathy related to a BAV are similar to what has been described in Marfan syndrome.⁴³ Some have suggested that management guidelines as described for Marfan syndrome should be applied to those with aortopathy related to a BAV (Class IIa, Level C2).^20,42

With assisted reproductive technology, women with Turner syndrome can now become pregnant. These women are at particular risk of dissection, relatively early in life,⁴⁴ even in the absence of recognized aortic root pathology or hypertension.⁴⁵ Pregnancy appears to significantly increase the risk of cardiovascular mortality.⁴⁶

Pressure overload lesions: right heart

Pulmonary stenosis

Unlike aortic stenosis, pulmonary stenosis (PS) is not associated with significant cardiovascular complications during pregnancy.^1,12,25 Two recent studies examining 68 women have reported no major cardiac complications.^47,48 One study also reported hypertension, thromboembolism and premature delivery in 15%, 4%, and 17% of pregnancies respectively.⁴⁸ Balloon valvuloplasty during pregnancy is feasible if symptoms of PS progress (Class I, Level C2).

Pulmonary vascular obstructive disease

Maternal mortality in Eisenmenger syndrome continues to be high and is approximately 30% in each pregnancy.⁵ Most complications occur at term and during the first week post partum. Current consensus is to advise against conception and to offer termination in the event of a pregnancy⁴⁹ (Class I, Level C1). The vasodilation associated with pregnancy will increase the magnitude of right-to-left shunting, exacerbating maternal cyanosis with adverse effect on fetal outcome. Consequently, these women are particularly sensitive to volume depletion and hypotension, situations which augment right-to-left shunting resulting in worsening cyanosis, hypoxemia and vasoconstriction. Overall, spontaneous abortion is common, intrauterine growth restriction is seen in 30% of pregnancies, and preterm labor is frequent. The high perinatal mortality rate (28%) is largely due to prematurity.

In an overview of 125 pregnancies in patients with Eisenmenger syndrome, primary and secondary pulmonary hypertension, maternal mortality was uniformly high at 36%, 30%, and 56% respectively.⁵ The overall neonatal mortality was 13%.

Cyanotic heart disease: unrepaired and repaired

In the absence of pulmonary hypertension, mortality associated with pregnancy is rare in women with uncorrected cyanotic congenital heart disease (CHD) although morbidity may be substantial.⁵⁰ The usual pregnancy-associated fall in systemic vascular resistance and rise in cardiac output exacerbate right-to-left shunting, leading to increased maternal hypoxemia and cyanosis. A study examining the outcomes of 96 pregnancies in 44 women with a variety of cyanotic congenital heart defects reported a high rate of maternal cardiac events (32%) and prematurity (37%) as well as a low livebirth rate (43%).⁵⁰ The lowest livebirth rate (12%) was observed in mothers with arterial oxygen saturation ≤85%.

Abnormalities of the systemic ventricle: systemic right ventricle and functional single ventricle

Transposition of the great arteries: systemic right ventricle

The original repair for ventriculo-arterial discordance or complete transposition of the great arteries (TGA) was the atrial switch procedure (Mustard or Senning operation). Contemporary surgical management has replaced the atrial switch procedure with the arterial switch operation (Jatene procedure). Virtually all published data regarding pregnancy in women with TGA are derived from women after atrial redirection. As the morphologic RV supports the systemic circulation, tricuspid regurgitation, RV dilation and RV dysfunction are commonly seen. Additional sequelae may include sinus node dysfunction, atrial tachyarrhythmia and baffle leak/obstruction.

Two retrospective studies of pregnancy post atrial redirection in 68 women (139 pregnancies) were recently published. The most commonly reported complications were arrhythmias (13–22%), CHF (7–15%) and maternal death/transplant (8%).^51,52 When serial echocardiography was utilized to examine impact of pregnancy on the systemic RV after the Mustard operation, progressive RV dilation occurred in 5/18 women (21%) and worsening RV function was noted in 4/21 (25%) women during pregnancy. At a mean follow-up 33 months after delivery, the RV remained enlarged in all five women (100%) and the RV dysfunction persisted in three-quarters of women (75%).⁵³ Although these data suggest that pregnancy may affect subsequent systemic RV function, these observations require confirmation using more objective and reproducible methods of RV quantification.

Women managed with an arterial switch operation have only recently reached child-bearing age and there are no published case series examining this population. However, in the absence of ventricular dysfunction, coronary obstruction, or other important residua or sequelae, a good outcome may be anticipated.

In congenitally corrected transposition, characterized by atrioventricular and ventriculo-arterial discordance (double discordance), the morphologic RV supports the systemic circulation. Consequently, tricuspid regurgitation and RV dilation and dysfunction are frequently seen. In two large studies of 105 pregnancies in 41 women, the most common complication was CHF (9–16%) and no maternal deaths were reported.^54,55

Fontan palliation: functional single ventricle

By surgically redirecting systemic venous return to the pulmonary arteries in those with single ventricle physiology, the Fontan palliation decreases volume overload on the systemic ventricle and reduces or eliminates cyanosis. However, there remains an inherent limitation in the heart’s ability to augment cardiac output. Long-term sequelae may include arrhythmia, ventricular dysfunction, protein-losing enteropathy and thromboembolic events. As the 10-year survival following the Fontan operation is only 60–80%, it is important that long-term maternal prognosis be discussed during preconception counseling.

In the largest series of pregnant women with Fontan palliation published to date, 33 pregnancies in 14 mothers were reviewed. The single cardiac complication reported in this study was supraventricular tachycardia in one woman.⁵⁶ In two subsequent studies examining 14 pregnancies in nine women, maternal cardiac complications included atrial tachyarrhythmia (three women), symptomatic ventricular dysfunction (two women), and right heart failure (two women); the rate of premature birth was high.^57,58 There have been no reported maternal deaths.⁵⁹

Rheumatic heart disease

Mitral stenosis (MS) is the most common rheumatic valvular lesion encountered during pregnancy. The hypervolemia and tachycardia associated with pregnancy exacerbate the impact of mitral valve obstruction. The resultant elevation in left atrial pressure increases the likelihood of atrial fibrillation.²¹ Thus, even patients with mild to moderate MS, who are asymptomatic prior to pregnancy, may develop atrial fibrillation and heart failure during the ante-partum and peripartum periods, contributing to substantial morbidity^1,12,25,60 Atrial fibrillation is a frequent precipitant of CHF in pregnant patients with MS. In a study of 80 pregnancies (moderate or severe MS in 47%), the first episode of pulmonary edema occurred at a mean gesta-tional age of 30 weeks and occurred in the setting of atrial tacharhythmias in 20%.⁶⁰

Percutaneous mitral valvuloplasty should be considered in patients with functional class III or IV symptoms despite optimal medical therapy and hospitalization^61–63 (Class I, Level C1).

Pregnant women whose dominant lesion is rheumatic AS have a similar outcome to those with congenital AS.

Peripartum cardiomyopathy

Peripartum cardiomyopathy is diagnosed by otherwise unexplained LV systolic dysfunction presenting during the last antepartum month or in the first five postpartum months.⁶⁴ Proposed echocardiographic criteria of LV systolic dysfunction include ejection fraction <45%, fractional shortening <30%, and end-diastolic dimension >2.7cm/m².⁶⁵ This entity can manifest as CHF, arrhythmia or embolic events. Many affected women will show improvement in functional status and ventricular function post partum, but others may have persistent or progressive dysfunction. The relapse rate during subsequent pregnancies is substantial in women with evidence of persisting cardiac enlargement or LV dysfunction. In a multicenter survey examining the outcomes of 60 pregnancies in women with peripartum cardiomyopathy diagnosed during a prior pregnancy, 44% of women with persistent LV systolic dysfunction (ejection fraction <50%) developed symptoms of CHF during subsequent pregnancies, with an associated mortality rate of 19%. In contrast, symptoms of CHF developed in 21% of women with normalized LV systolic function (ejection fraction ≥ 50%) and none of this group died.⁴ For women who are planning on another pregnancy, angiotensin-converting enzyme inhibitors should be avoided due to their teratogenic effects.⁶⁶ In another survey of 100 pregnancies in women with peripartum cardiomyopathy and no subsequent pregnancies, the majority of cases (75%) were diagnosed in the first month postpartum; normalization of LV systolic function occurred in 54% and was more likely if ejection fraction was >30% at diagnosis.⁶⁷ These authors suggest that the criteria for diagnosis of peripartum cardiomyopathy based on timing of presentation may be unnecessarily restrictive as those with “pregnancy-associated cardiomyopathy” diagnosed earlier in pregnancy are indistinguishable in terms of baseline characteristics and outcome.⁶⁷ Women with peripartum cardiomyopathy and significant residual LV dysfunction are advised against further pregnancies (Class I, Level C1).

Hypertrophic cardiomyopathy

In patients who have either resting or provocable LV outflow tract obstruction, the degree of LV outflow tract obstruction during pregnancy is variable and is a result of interplay between increases in preload (which reduces severity of obstruction) and decreases in afterload (which worsens obstruction). Diastolic dysfunction magnifies preload dependence of cardiac output and may result in worsening symptoms even in the absence of LV outflow tract obstruction.

Maternal outcomes are often good, though several deaths have been reported, and serious complications (CHF, tachyarrhythmias, syncope) may occur, especially in women with preconceptual symptoms, and in those with substantial LV diastolic and/or systolic dysfunction or significant LV outflow tract obstruction. In a multicenter retrospective review of 199 pregnancies, there were two sudden deaths in women known to be at high risk who were counseled against pregnancy (one with severe LV outflow tract obstruction and symptomatic heart failure and one with a malignant family history); clinical decompensation during pregnancy occurred in 15% and was significantly associated with prepregnancy functional class.⁶⁸ In a recent single-center retrospective review of 271 pregnancies, there were no maternal deaths and >90% of women with cardiac symptoms during pregnancy experienced cardiac symptoms prior to pregnancy; symptomatic deterioration occurred in <10%.⁶⁹ Fetal outcomes are good. Beta-blockers may be used, as in the non-pregnant state. Dual-chamber pacing may be of value in patients with symptoms refractory to medical therapy (Class IIb, Level C2). The role of septal alcohol ablation or surgical myectomy during pregnancy has not been defined.

Coronary artery disease

The risk of myocardial infarction (MI) appears to be increased by pregnancy. A study examining hospital discharge data of >23 million pregnancies between 2000 and 2002 determined that the incidence of pregnancy-related acute MI in pregnancy was 6.2/100 000 deliveries with a mortality rate of 0.35/100 000 deliveries.⁷⁰ Of 859 cases of acute MI related to pregnancy reviewed, 73% occurred during pregnancy and 27% occurred post partum necessitating readmission to hospital. The risk of acute MI was 3–4 times higher in pregnancy as compared with the published incidence of MI among reproductive-aged women. Risk factors for MI included advanced maternal age, hypertension, diabetes mellitus, smoking, thrombophilia, need for transfusion and postpartum infection. Earlier studies demonstrating lower incidences of MI may relate to better ascertainment in recent studies, improved diagnosis related to widespread troponin use, or increased number of pregnancies in older women.^71,72 Guidelines for the cardiopulmonary resuscitation of the pregnant patient have been recently published.⁷³

Diagnosis of infarction may be confounded peripartum because of release of CK-MB isoenzyme from the uterus.⁷⁴ Thromobolysis is not contraindicated⁷⁵