Women who have had miscarriages are often given blood tests to check for genetic problems that may lead to blood clots.
These inherited clotting problems affect about 1 in 10 people in North America, according to study researcher Marc Rodger, MD. He is a senior scientist at the Ottawa Hospital Research Institute in Canada.
The fear is that having one of these clotting problems may cause clots to form in the placenta, choking the delivery of oxygen and nutrients to a growing baby.
Research in the past suggested that having a clotting disorder might be tied to miscarriage, so about 15 years ago doctors began to prescribe the blood thinner heparin, which is sold under the brand names Fragmin, Innohep, and Lovenox, to help prevent them and other serious problems like preeclampsia.
“And that led to a lot of docs prescribing this medication and a lot of patients demanding this medication, because there’s really very little that can be offered to [these] patients,” Rodger says.
In the new study, which is published in The Lancet, doctors recruited 292 pregnant women who had clotting disorders confirmed by blood tests. They were also considered to be at high risk for pregnancy complications because they had a history of preeclampsia, pregnancy loss, blood clots in a leg or lung, a low-birth-weight baby, or a placental abruption, where the placenta separates from the wall of the uterus before delivery.
Researchers randomly assigned about half the women to get daily injections of the blood thinner Fragmin. The other half didn’t get the injections. Most started the injections around the 12th week of pregnancy and continued until week 37.
About 1 in 6 women in the study had a serious pregnancy complication during the study. Those included blood clots, high blood pressure and mild kidney failure, birth of a baby that was small for its age, or a miscarriage.