Pregnant women with a history of thrombosis or pulmonary embolisms are often prescribed unnecessary amounts of medication. This is likely to change all around the world, thanks to a Radboudumc researcher.

For years, internist Saskia Middeldorp at the Radboudumc was bothered by the wild variation in prescription policies. ‘Hospital A might give you one dosage and Hospital B will give an entirely different one. Nobody really knew the right method; treatment became a kind of lottery’, says the professor and head of the internal medicine department.

Her research shows a lot of hospitals prescribe double the required dosage of anticoagulants to pregnant women who have suffered from thrombosis or a pulmonary embolism. That is not just needlessly expensive, but also leads to more side effects and makes it more difficult to administer an epidural during labour.

Clogged artery

Women with a history of clogged arteries are prescribed anticoagulants because they are more likely to develop a blood clot in their veins or lungs over the course of their pregnancy; Thrombosis and pulmonary embolisms are the leading causes of death in pregnant women.

A daily shot of the anticoagulant heparine can help to prevent thrombosis, but nobody knew how much of heparine was needed. Sometimes, doctors used the normal dosage for someone undergoing surgery, even though pregnant bodies process medication in a vastly different way.

‘Anticoagulants are not a pleasant treatment’

That is why Middeldorp shadowed 1100 women in nine different countries during their pregnancies and the six weeks post-partum. Half of them were prescribed a lower dosage, while the other half was prescribed a double dosage. The chance of developing a blood clot proved to be the same for both groups, which means that lower dosages suffice. ‘That is very good news’ according to Middeldorp, who spent ten years working on the study, ‘because anticoagulants are not a pleasant treatment.’

However, a higher dosage did prove more effective for women in their postpartum period – the first few weeks after giving birth. That period has the highest risk of thrombosis, but it is not yet clear why that is.

New thrombosis

Middeldorp’s research, which has now been published in the prestigious medical journal The Lancet, also showed that 2-3% of women developed new thrombosis despite medication. ‘That is very good to know, because that is something you can inform the patient of.’

Middeldorp, who is a part of several international committees that make treatment protocols, expects that the lower dosage will become the new world standard.

This article was translated by Jasper Pech. The Dutch originally was written by Eric Reijnen Rutten and was previously published in de Gelderlander.