A daily injection to the belly for pregnant women at risk of developing blood clots is ineffective, according to a study by researchers at the Ottawa Hospital.
“It’s very typical that women are willing to take risks for the pregnancy for the potential benefit,” said senior scientist Dr. Marc Rodger, head of TOH’s thrombosis program.
Results from a 12-year randomized clinical trial involving 296 women worldwide were published Thursday by The Lancet medical journal.
Roughly one in 10 women have a tendency to develop thrombophilia, or blood clots in their veins, posing complications during pregnancy.
The anticoagulant low molecular weight heparin (LMWH) is commonly prescribed to prevent clotting and warrants up to 400 needles during a pregnancy.
The study provides conclusive evidence that LMWH has no positive benefits for the mother or child.
During Rodger’s trial some women received the needles, others didn’t.
The procedure is expensive, costing $4,000 in Ontario per pregnancy.
It’s not covered by OHIP, said Rodger, noting private insurance may cover treatment, which goes for $8,000 in the U.S.
The study finds the injection — painful, causing bruises — potentially caused minor harm by increasing bleeding, rates of induced labour, and reducing access to anesthesia during childbirth, meaning this risk was unnecessary.
About 20 years ago, using LMWH to treat pregnant women became commonplace, said Rodger, despite the fact a large, multi-site randomized clinical trial never proved its effectiveness.
“A lot of people kind of jumped on the bandwagon,” said Rodger.
Allison McIntosh, a 34-year-old Ottawa lawyer, had two miscarriages and was prescribed LMWH during her third pregnancy.
After 10 weeks of injecting herself daily, she miscarried again.
“I thought that I was doing something to make a difference by giving myself the injections,” said McIntosh.
“I kind of lost hope after that experience.”
Now six months along in her fourth pregnancy, McIntosh and husband Jeremy Gaudet have decided to pass on injections.
“I feel sad for other people who are going through that process,” said McIntosh.
“It can be disillusioning for people if those injections are their only hope.”
LMWH is also prescribed to women, with and without thrombophilia, to prevent placenta blood clots that may lead to pregnancy loss, as well as high blood pressure, heavy bleeding, and low birth weight babies.
Rodger said he was surprised by the findings.
“We did get into this to be able to show that this therapy worked,” he said.
“We want to offer something to these patients that have these horrible complications.”
Blood thinners may be effective for one type of thrombophilia, and some women are advised to take low-dose aspirin while pregnant.