Mechanical Valves in Pregnancy: A Sticky Business
Caring for women with mechanical heart valves (MHVs) in pregnancy poses one of the greatest clinical challenges in our specialty. Pregnancy is a prothrombotic state due to relative increases in fibrinogen, plasminogen activator inhibitors, clotting factors, Von Willebrand factor and platelet adhesion molecules, and concomitant decreases in protein S activity. These hypercoaguable changes begin in early pregnancy and persist for at least 6 to 12 weeks postpartum. Evidence from contemporary and historical cohorts of women with mechanical valves in pregnancy suggests increased risk of maternal cardiovascular events, obstetric morbidity such as hemorrhage and preterm birth, and fetal complications including growth restriction, miscarriage, and stillbirth. Owing to these risks, pregnant women with mechanical valves need rigorous control of their anticoagulation; however, the ability to achieve meticulous anticoagulation is hampered by the increased renal clearance and volume of distribution associated with pregnancy. Thus, pregnant women are at the highest risk for complications of mechanical valves at a time when it is the most difficult to maintain adequate anticoagulation. In caring for these women, we strive for a balance between the maternal risk of valve thrombosis, systemic thromboembolism, and hemorrhage with the fetal risk of exposure to oral vitamin K antagonists (VKAs).
- Received June 7, 2015.
- Accepted June 17, 2015.