Women with a mechanical prosthetic heart valve were at greater risk of pregnancy complications compared with women with a biological valve, based on findings from the ROPAC III study published April 16 in the European Heart Journal. Additionally, the large global study found use of low molecular weight heparin (LMWH) increased the risk for thromboembolic complications compared with other anticoagulation regimens.

A total of 613 pregnancies in 585 women with prosthetic heart valves from 27 countries (average age of 30 years) were included in the study. Of these pregnancies, 411 were in women with a mechanical valve and 202 were in women with only a biological valve. Broken down by country, 81% of the pregnancies in women with a mechanical valve were from a low- or middle-income country (LMIC), compared with 38% of the pregnancies in women with a biological valve (p<0.001).

Overall results found the odds of having an uncomplicated pregnancy with a live birth were 54% in those with a mechanical vs. 79% in those with a biological valve (p<0.001). Fetal death occurred in 27% of women with a mechanical valve compared with 6% of those with a biological valve.

Findings also showed greater risk of thromboembolic (9% vs. 2%) and hemorrhagic (20% vs. 9%) events in women with a mechanical valve. Of note, a mitral valve prosthesis was found to be a predictor for valve thrombosis (odds ratio, 3.3; 95% CI, 1.9-8.0), while BMI was an independent predictor of any thromboembolic event (hazard ratio, 1.1; 95% CI, 1.0-1.1).

"We identified a mitral prosthetic valve and BMI as a predictor for valve thrombosis and any thromboembolic event, respectively, and these women should be followed even more carefully with a low threshold to perform imaging including TEE," write Johanna A. van der Zande, et al.

Researchers also tracked anticoagulation use before and throughout pregnancy, dividing participants into four regimens: 1) Vitamin K antagonist (VKA) throughout pregnancy; 2) LMWH throughout pregnancy; 3) Change to unfractionated heparin (UFH) early in pregnancy and switch to VKA in second trimester; and 4) change to LMWH early in pregnancy and switch to VKA in second trimester.

Researchers found that strategies varied by country with warfarin and UFH predominantly used in LMICs, compared with higher-income countries. While these regimens tended to have better thromboembolic and hemorrhagic outcomes, fetal death rates were higher, according to van der Zande and colleagues.

Overall, thromboembolic events were more frequent in women taking LMWH. However, while a higher rate of thromboembolic events in women without a plan for anti-Xa level monitoring (21%) was observed compared with women with a plan for monitoring (10%), statistical significance was not reached.

"On the basis of our findings, we conclude that it is reasonable to maintain the status quo as contained in the current guidelines and continue to recommend anti-Xa monitoring of LMWH treatment if possible, on the basis that it is highly unlikely to be harmful," write the authors. "...There is a definite possibility that in some individual cases, it may be beneficial in avoiding anticoagulation levels falling too low or being excessive."