Most clinically signiicant congenital heart lesions are repaired during childhood. Examples of those frequently not diagnosed until adulthood include atrial septal defects, pulmonic stenosis, bicuspid aortic valve, and aortic coarctation (Brickner, 2014). In some cases, the defect is mild and surgery is not required. In others, a significant anomaly is amenable to corrective surgery, performed ideally before pregnancy. In rare instances, surgical corrections are necessary during pregnancy.
Numerous reports describe subsequent pregnancy outcomes in women who have a prosthetic mitral or aortic valve. The type of valve, either mechanical or biological, is paramount. From one review, the overall estimated maternal mortality rate was 1.2 percent. he rate was 1.8 percent in the mechanical valve subgroup and 0.7 percent in the bioprosthetic subgroup (Lawley, 2015). Using the Registry of Pregnancy and Cardiac Disease, the maternal mortality rate was 1.4 percent in women with a mechanical heart valve and 1.5 percent in women with a tissue heart valve (van Hagen, 2015). Mechanical heart valve thrombosis complicated 4.7 percent. In total, only 58 percent with a mechanical heart valve had a pregnancy free of serious adverse events compared with 79 percent of patients with a tissue heart valve (Table 49-5). Because of thrombosis risks, anticoagulation may be requisite, but its complications are described in the next section. Thus, pregnancy is undertaken only ater serious consideration for women with a prosthetic mechanical valve.
Bouhout and coworkers (2014) reported the outcomes of 27 pregnancies in 14 women who underwent an aortic valve replacement prior to pregnancy. Seven of the 27 pregnancies occurred in five women with a mechanical prosthesis. Complications in this group included two embolic myocardial infarctions and one each of miscarriage, postpartum hemorrhage, placental abruption, and preterm birth. In the bioprosthetic group, nine miscarriages, two hospitalizations for syncope, and one preterm birth were noted.
Porcine tissue valves are safer during pregnancy, primarily because thrombosis is rare and anticoagulation is not required (see Table 49-5). Despite this, valvular dysfunction with cardiac deterioration poses a serious risk. Another drawback is that bioprostheses are less durable than mechanical ones, and valve replacement longevity averages 10 to 15 years. Cleuziou and colleagues (2010) concluded that pregnancy does not accelerate the risk for replacement. But, Nappi and associates (2014) found an association between pregnancy and valve deterioration in women with cryopreserved mitral homograft valves.
his is critical for women with mechanical prosthetic valves . Unfortunately, warfarin is the most efective anticoagulant for preventing maternal thromboembolism but causes harmful fetal efects (Chap. 12, p. 247). Anticoagulation with heparin is less hazardous for the fetus, however, the risk of maternal thromboembolic complications is much higher (McLintock, 2011).