National study funded by Wellbeing of Women, identifies that improvement in care is needed for pregnant women with mechanical prosthetic (artificial) heart valves
A study has been published in the BJOG which shows that for some pregnant women with mechanical prosthetic heart valves, improvements in care could lead to better outcomes for both mother and baby.
Anyone with a prosthetic heart valve needs to take drugs to thin the blood for the rest of their lives. The two most popular drugs are Warfarin (a tablet taken by mouth) and Heparin (by injection only).
Women with these prosthetic heart values pose a particular problem because blood is stickier in pregnancy so the risk of the valve clotting is higher and the need for effective blood thinning is greater. Warfarin, the usual drug, can cause abnormalities and problems with brain development in unborn babies. Heparin and in particular low molecular weight heparin (LMWH) doesn’t cross the placenta, so is safe for the unborn baby, but some doctors believe this drug is not as effective at protecting the mother against blood clots on her heart valve.
A 2 year study, from Feb 2013 to January 2015, funded by Wellbeing of Women was led by Dr Sarah Vause at the Central Manchester University Hospitals to find out what sorts of problems occur in women with prosthetic valves using the different blood thinning drugs and whether their baby had any problems.
Using the data collection system established by UKOSS (UK Obstetric Surveillance System) collecting data from every hospital in the UK, hospitals were asked to report on any woman who had been pregnant with a prosthetic heart valve.
There were 58 women who got pregnant with a mechanical prosthetic heart valve confirming it is a rare condition with sadly five (9%) resulting in maternal deaths and a further 41% suffering serious complications. Most women (71%) took LMWH and most of these women (83%) had their normal dose increased rapidly in early pregnancy, suggesting the standard recommended dose is insufficient for pregnant women. The study also revealed that only 28% of pregnancies resulted in a good outcome for both the mother and baby.
The study recommends the following improvements to the care of some women and these are:
- The need for doctors caring for women of reproductive age, with prosthetic valves, to ensure that they have preconceptual counselling and are aware of the need to seek medical advice as soon as they find out they are pregnant.
- If a woman chooses to use LMWH, then she should be started on a dose higher than that currently recommended in the British National Formulary
- Women should be looked after in specialist centres, by multidisciplinary teams, so that a smaller number of doctors gain more experience in looking after them.
Dr Sarah Vause and her colleagues will continue to present their work nationally and internationally to cardiologists, haematologists and obstetricians. They’re also keen to present their findings to patient groups so that the women themselves are aware of all the information.