Research shows poor maternal and fetal health outcomes in pregnant women with mechanical prosthetic heart valves

Research led by consultants at Central Manchester University Hospitals NHS Foundation Trust (CMFT) shows that pregnant women with mechanical prosthetic heart valves (MPHVs) have poor maternal and fetal health outcomes.

During pregnancy women with MPHVs are more prone to forming clots on their mechanical valve, which can block it or cause the woman to have a stroke.  Some anticoagulants, which are used to prevent clots, can cause fetal abnormalities, and all anticoagulants make women more prone to bleeding, which is a particular problem around the time of delivery.

A study led by Dr Sarah Vause, Consultant in Fetal and Maternal Medicine at CMFT, collected data on how many women with MPHVs got pregnant in the UK each year and the rates of maternal and fetal complications in this group of women. It also aimed to determine whether these complication rates vary with anticoagulation treatment used during pregnancy.

It found that of the 58 pregnancies in women with MPHVs recorded in the UK during the two-year study, five (9%) resulted in maternal deaths and a further 41% of women suffered serious maternal complications. Just 28% of pregnancies resulted in a good outcome for both mother and baby.

Most women (71%) used Low Molecular Weight Heparin (LMWH) as their anticoagulant during pregnancy, and 83% of these had their normal dose increased rapidly in early pregnancy, suggesting the standard recommended dose may be insufficient for pregnant women.

Authors of the report recommend that women of reproductive age with MPHVs should have preconceptual counselling to ensure that they understand the significant risks they will be taking if they decide to embark on pregnancy. During pregnancy, care for this group of women should be delivered by specialist centres.

Data from the study has also been used in the 2016 MBRRACE maternal mortality report. This national report makes recommendations for practice, and is widely read by clinicians involved in the care of pregnant women.

Wellbeing of Women, a charity supporting research in women’s reproductive health and childbirth, funded the study.

The full report has been published in journal BJOG.

Dr Sarah Vause said:

We hope that clinicians will incorporate the messages from the study into their practice, and that this will not only reduce maternal and fetal morbidity, but may prevent women with MPHVs from dying.