New data on DOAC exposure in pregnancy – cause for alarm?

New data on outcomes from pregnancies with early DOAC exposure is both alarming and reassuring on different levels, European clinicians say.

Professor Jan Beyer-Westerndorf, head of thrombosis research at the University Hospital Dresden in Germany, told the ISTH 2020 Virtual Congress that his team have identified 593 separate cases of drug exposure in pregnancy with a mean duration of DOAC exposure of about seven weeks.

Speaking in a state-of-the-art session on women’s health, he said of the 316 known pregnancy outcomes there were 175 live births (55.4%), 69 miscarriages (21.8%) and an alarming 72 elective pregnancy terminations (22.8%).

“The most common reason given for this [number of terminations] was an unknown risk of safety or embryotoxicity of this early pregnancy DOAC exposure. Obviously, this unresolved issue has a huge medical and ethical dimension,” he said.

On the other hand the study found very few non-suspicious abnormalities in live births (n=4), miscarriages (n=3) and elective pregnancy terminations (n=1).

“We found some 12 abnormalities where we could not rule out a potential for embryotoxicity –  12 out of 316 translates into an overall worse case rate of 3.8% which is quite reassuring because it is lower than the reported 5-7% for warfarin exposure.”

“Even more reassuring from our perspective is the fact that we could not identify a distinct pattern of abnormalities, which is very different from warfarin embryopathy where the abnormalities follow a very strict pattern.”

Professor Beyer-Westerndorf said the 2016 guidance statement from the ISTH recommended a switch from DOACs to an alternative anticoagulant preconception in the case of a planned pregnancy and an immediate switch to LMWH in the case of an unintended pregnancy while on DOAC.

However “inadvertent exposure to a DOAC is not sufficient grounds for termination of a pregnancy,” he said, and instead, early obstetric review and foetal monitoring is recommended.

Professor Beyer-Westerndorf said his practice with women on a DOAC who plan to become pregnant was to first reassess their need for anticoagulants and consider aspirin as an alternative because it has been shown to reduce risk of recurrent VTE.

“If continued anticoagulation is recommended, and the patient is concerned about a lack of DOAC safety data, then I would switch the patient to LMWH preconception.”

“If heparin is not possible on medical grounds, or not accepted by the patients, based on available data I would consider keeping the patients on a DOAC until pregnancy is confirmed and then switch patients to LMWH, but this strategy depends on an early diagnosis of pregnancy.”

He said a final strategy was to consider switching the patient to a VKA until the pregnancy was confirmed and then to LMWH.

However the established embryotoxicity risk of 5-7% with warfarin limits this to a back-up strategy only.

The data updates a smaller 2016 study which also found no evidence that DOAC exposure in pregnancy carried a high risk of embryopathy.

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