Management Guidelines

Pre-pregnancy Counseling

Asymptomatic women with only a mild stenosis in casu aortic valve area >1.5cm and/or a mean Doppler gradient in the LVOT of less than 30mmHg can be considered low-risk and should have appropriate pre-pregnancy counseling in a specialized environment. However, they can generally be managed in a conservative way at their local hospital. AS patients with a valve area >1cm and/or a mean Doppler gradient in the LVOT of less than 50mmHg and preserved systolic left ventricular function will tolerate pregnancy well. In the absence of complications, the pregnancy can be followed in the local hospital, but a more specialized center is preferred for delivery.^18,19 In all other cases (valve area <1cm), antenatal care and care during pregnancy should take place in a tertiary care clinic with a multidisciplinary approach involving geneticists, cardiologists, obstetricians, and anesthesiologists. In pre-pregnancy counseling, an exercise test is advised to rule out ST-T changes and arrhythmia. Patients with valve-related symptoms or extremely severe AS should be advised to delay conception until relief of the obstruction. Nevertheless, selection of valve prostheses for women of childbearing age is still a major issue. Bioprostheses are not as durable as mechanical prostheses, but eliminate the risks associated with anticoagulation for mechanical valves. Bioprosthetical valves do not seem to degenerate more rapidly during pregnancy, as was previously feared.²⁰ The Ross procedure, which has a better long-term outcome, is an attractive option for women of childbearing age.

Pregnancy

Asymptomatic pregnant women with severe AS have to be managed in a conservative way with bed rest, beta-blockers, and diuretics. However, in patients who develop alarming symptoms and who are resistant to medical treatment and reluctant to terminate their pregnancy, percutaneous balloon valvuloplasty or surgery before labor and delivery might be an option. However, aortic valve surgery is associated with a high risk of fetal loss (up to 30%), and, therefore, percutaneous valvuloplasty is mostly preferred.^21,22 If the fetus is viable, a Cesarean section can be performed immediately before surgical valve repair or replacement.

Delivery

In most cases, vaginal delivery with assisted second stage of labor is recommended; this comprises low-dose epidural analgesia with a cardiostable drug, labor in left lateral decubitus to avoid aortocaval compression, and obstetric procedures such as vacuum extraction or forceps to shorten the second stage and to avoid repetitive Valsalva maneuvers. A Cesarean section is mainly preserved for obstetric indications; cardiac reasons for a Cesarean section include an aortic root dilatation of more than 4cm, aortic aneurysm, or high risk of aortic dissection or rupture. Hemodynamic monitoring during labor and delivery is strongly recommended in women with moderate to severe aortic valve stenosis. Low-dose epidural anesthesia with adequate volume expansion to avoid a sudden decrease in systemic vascular resistance is allowed in these patients.23 Although the American Heart Association (AHA)/American College of Cardiology (ACC) and European guidelines do not advise antibiotic prophylaxis in non-instrumented vaginal delivery or Cesarean section, most practitioners routinely provide antibiotics at the onset of labor. Indeed, bacteremia is reported in 2% of the patients, even after an uncomplicated vaginal delivery.²⁴

Anticoagulation During Pregnancy

In the absence of residual hemodynamic lesions, pregnancy and delivery are generally well tolerated after valve replacement. However, the need for anticoagulation therapy for mechanical valve prostheses represents a major problem. There are no randomized trials available to compare different anticoagulation regimens during pregnancy. Recommendations are largely based on extrapolations from data derived from series of non-pregnant patients and from small case series of pregnant patients. Substantial concern remains about the fetal safety of warfarin, since it crosses the placenta and might cause the typical warfarin embryopathy. However, the incidence of this embryopathy is still an issue for debate. The overall risk seems to be around 5% in patients who receive vitamin K antagonists between the sixth and 12th week, but seems to be significantly lower if the dose of warfarin is less than or equal to 5mg/day. On the other hand, a recent overview of the literature reported an increased risk of maternal thromboembolism when using heparin, even in anti-Xa adjusted doses.²⁵ Warfarin therapy is still the safest option for the mother and is associated with a 4% rate of maternal thromboembolism and a 30% rate of fetal loss. The strategy of substituting heparin for warfarin during the first trimester eliminates the risk of warfarin embryopathy, but doubles the risk of thromboembolism for the mother up to 9%. However, fetal loss rates are similar for any method of effective anticoagulation. Whatever the regimen of anticoagulation chosen during pregnancy, strict follow-up and frequent monitoring for appropriate dose adjustment are mandatory.¹⁹

In summary, most women with mild to moderate aortic valve stenosis may have a relatively low-risk pregnancy. Therefore, to identify these patients, pre-pregnancy counseling should be optimized, starting from adolescence. The latter gives the opportunity to tailor advice to the individual patient in order to prevent avoidable pregnancy-related risks. Related to the problems of pregnancy, women of reproductive age should also be informed about contraception. Finally, adequate care during pregnancy and delivery and in the postpartum period requires a multidisciplinary approach by cardiologists, obstetricians, geneticists, and anesthesiologists.