Anticoagulation of Pregnant Women with Mechanical Heart Valve Prosthesis: A Systematic Review of the Literature (2000–2009)

Review Article

Anticoagulation of Pregnant Women with Mechanical Heart Valve Prosthesis: A Systematic Review of the Literature (2000–2009)

Ahmed Hassouna ¹ and Hemat Allam ²
Affiliations: ¹Ain-Shams University, Cairo, Egypt and ²National Research Center, Cairo, Egypt


ABSTRACT

Managing anticoagulation of pregnant women with mechanical heart valve prosthesis (MPHV) is now mainly limited to three alternatives: oral anticoagulants (OA) throughout pregnancy; oral anticoagulants substituted by heparin between the 6th and 12th week of gestation then resumed thereafter (OA/H); and heparin—either unfractionated or low molecular weight—throughout pregnancy. We performed a systematic review and calculated pooled estimates (95% confidence interval) of adverse fetal and maternal outcomes for the three regimens, as well as for a fourth group of concomitantly reported patients who stopped all anticoagulation, against medical advice. Events were expressed as proportions of total pregnancies, except embryopathy and maternal death, which were related to the numbers of live births and number of patients respectively. There were 1343 eligible pregnancies, 62% of which followed the OA regimen. The low‐dose warfarin adopted by most authors may be responsible for the low rate of fetal malformations: 3.7% (95% CI 1.9–4.8%). In OA/H patients, embryopathy became negligible: 0.4% (95% CI 0.2–2.7%), and the rates of spontaneous abortions and total fetal wastage dropped by around 40% from 23.3% (95% CI 13.8–31.6%) and 32.9% (95% CI 25.7–49.2%) in OA patients to 13% (95% CI 7–21.6%) and 19.9% (95% CI 15.9–31.4%) respectively. Such positive effects disappeared with the continuation of heparin until parturition. The pooled proportions calculated for prosthetic valve thrombosis, all thromboembolic complications, and maternal mortality in OA patients, 1.2% (95% CI 0.7–2.2%), 2.9% (95% CI 1.4–4.9%), and 1.1% (95% CI 0.5–2.2%), were doubled in OA/H patients, 5.3% (95% CI 3–10.8%), 7.1% (95% CI 4.7–10.3%), and 1.7% (95% CI 0.8–4.5%) and almost quadrupled in heparin‐treated patients, 10.2% (95% CI 6.9–16.9%), 13.4% (95% CI 9.7–20.5%), and 4.7% (95% CI 2.2–10.7%) respectively. This study shows that OA and OA/H are still competing alternatives for pregnant women with MPHV, especially with an apparently decreasing rate of fetal embryopathy. Heparin does not ensure better fetal outcomes and is still associated with the worst adverse maternal outcomes, including mortality. Still, the three regimens need more detailed reporting on anticoagulation levels and adjustments. We do not have enough data to evaluate the effect of adjuvant antiplatelet therapy.

Keywords: systematic review, pregnancy, mechanical prosthetic heart valve, oral anticoagulants, heparin, antiplatelet
Correspondence: Ahmed Hassouna, PO Box 93, Elmukattam, 11571 Cairo, Egypt. Tel: (2012)‐310‐5271; e‐mail: ahmedhassouna@hotmail.com