The use of low molecular weight heparin in pregnant women with mechanical and bio-prosthetic heart valves: An eight-year experience at an academic hospital

Abstract

Pregnancy in women with mechanical prosthetic heart valves (MPHV) is a significant contributor to maternal morbidity and mortality worldwide. This requires individualized management to safely balance the maternal and fetal risks associated with the various anticoagulation strategies. A descriptive cross-sectional study was performed to review the maternal and fetal outcomes in pregnant women with prosthetic heart valves managed according to a protocol recommending low molecular weight heparin (LMWH) throughout pregnancy in order to provide guidance on the management of this high risk population. Fifty pregnancies with MPHV and three with tissue valves, on anticoagulation for comorbid atrial fibrillation, attending the Specialist Cardiac Antenatal Clinic at the Charlotte Maxeke Johannesburg Academic Hospital between 1 July 2015 and 30 June 2023 were included. The majority were of African ethnicity at a mean age of 33 ± 6 years. Anti-Xa adjusted enoxaparin was commenced at 10.5 ± 5.6 weeks’ gestation until delivery in 48 (90.6%) pregnancies and warfarin was continued in 5 (9.4%) pregnancies. The live birth rates on enoxaparin and warfarin were 56.3% (95% confidence interval [CI] 42.3-69.3) and 20.0 % (95% CI 2.0-64.0) respectively. There were 12 (22.6 %) miscarriages at a mean of 11.3 ± 3.7 weeks’ gestation, 4 (7.5%) intra-uterine fetal deaths on warfarin and 2 (3.8%) warfarin embryopathy/fetopathy. The rates of antepartum/secondary postpartum bleeding and primary postpartum bleeding were 29.4% (95% CI 18.6-43.1) and 5.9% (95% CI 1.4-16.9) respectively. Maternal complications included anaemia (n=11, 20.8%), arrhythmia (n=2,3.8%), heart failure (n=2, 3.8%) and para- valvular leak (n=2, 3.8%). There was one (1.9%) mitral valve thrombosis and one (1.9%) stuck valve in pregnancies who defaulted warfarin prior to pregnancy. There were no maternal deaths. Multidisciplinary management of pregnant women with MPHV with anti-Xa adjusted v LMWH throughout pregnancy represents an effective anticoagulation option for low-middle- income countries.