COMMON BLOOD THINNER FOR PREGNANT WOMEN PROVEN INEFFECTIVE
It's a daily injection
to the belly for pregnant women at risk of developing blood clots and it's
ineffective, according to a clinical trial led by researchers at The Ottawa
Hospital and published today by the medical journal The Lancet.
As many as one in 10
pregnant women have a tendency to develop blood clots in their veins, a
condition called thrombophilia. For two decades these women have often been
prescribed the anticoagulant low molecular weight heparin (LMWH) to prevent
pregnancy complications caused by placental blood clots. This treatment
requires women to give themselves daily injections -- a painful and
demoralizing process that requires women to poke their abdomen with hundreds of
needles over the course of their pregnancy.
Now, a randomized
clinical trial led by Dr. Marc Rodger, a senior scientist at the Ottawa
Hospital Research Institute who heads up the Thrombosis Program of The Ottawa
Hospital, provides conclusive evidence that the commonly prescribed LMWH
anticoagulant has no positive benefits for the mother or child. In fact, Dr.
Rodger's study shows that LMWH treatments could actually cause pregnant women
some minor harm by increasing bleeding, increasing their rates of induced
labour and reducing their access to anesthesia during childbirth.
"These results
mean that many women around the world can save themselves a lot of unnecessary
pain during pregnancy," says Dr. Rodger, who is also a professor in the
Faculty of Medicine at the University of Ottawa. "Using low molecular
weight heparin unnecessarily medicalizes a woman's pregnancy and is
costly."
Since the 1990s, using
LMWH to treat pregnant women with a tendency to develop blood clots became
commonplace, despite the fact that a large, multi-site randomized clinical
trial had never been conducted to prove its effectiveness. Low molecular weight
heparin is also prescribed by many physicians worldwide to women, with and
without thrombophilia, to prevent placenta blood clots that may lead to
pregnancy loss, as well as preeclampsia (high blood pressure), placental
abruption (heavy bleeding) and intra-uterine growth restrictions (low birth
weight babies). The anticoagulant LMWH is also prescribed to prevent deep vein
thrombosis (leg vein blood clots) and pulmonary embolisms (lung blood clots).
"While I wish we
could have shown that LMWH prevents complications, we actually proved it
doesn't help," adds Dr. Rodger. "However, I'm very glad that we can
now spare these women all those unnecessary needles."
Allison McIntosh, a
34-year-old lawyer with the Department of Justice in Ottawa, knows the pain and
dejection that people feel who pin their hopes of carrying a baby to term on
the LMWH injections. After twice miscarrying, Ms. McIntosh was prescribed LMWH during
her third pregnancy. She spent two-and-a-half months giving herself a needle
every day only to find out the treatment didn't work when she miscarried for a
third time.
"It was difficult
after realizing that the injections didn't work," says Ms. McIntosh.
"I thought that I was doing something to make a difference by giving
myself the injections. I kind of lost hope after that experience."
Now pregnant for a
fourth time, Ms. McIntosh says that she and her husband Jeremy Gaudet, decided
to forgo LMWH or any other injections this time around. Furthermore, she says
that she is not surprised to hear that LMWH has been disproven as a means of
preventing blood clots in pregnant women.
"I feel sad for
other people who are going through that process," says Ms. McIntosh, who
is now six months along in her latest pregnancy. "It can be disillusioning
for people if those injections are their only hope."
Amy Mills, a
35-year-old mother of two young children, agrees with Ms. McIntosh and is
relieved to hear that LMWH treatments have been disproven. Ms. Mills, who lives
in Bancroft, Ontario, participated in Dr. Rodger's clinical trial after it was
discovered that she is prone to developing blood clots. Prescribed LMWH by her
doctor, Ms. Mills gave herself more than 400 needles full of the anticoagulant
medication during the course of her pregnancy -- often two needles a day. The
process resulted in severe bruising and pain, says Ms. Mills, who works as a
manager at McCaskie TV & Stereo in Bancroft.
"It hurt each and
every time I injected myself," says Ms. Mills of the experience.
"Most women are proud to show their pregnancy belly, but not me. There was
so much bruising I had to keep covered up."
Today, Ms. Mills and
her carpenter husband Jeff are the proud parents of seven-year-old Mikayla and
five-year-old Joshua. Ms. Mills says she is glad that she participated in Dr.
Rodger's study as it means other women won't have to go through what she
endured. She adds that to prevent the development of blood clots during her pregnancy
with second child Joshua, she merely took Baby Aspirin each day.
Dr. Rodger's clinical
trial took 12 years to complete and involved 292 women at 36 centres in five
countries. The study's results were published online today and will appear in a
future print issue of The Lancet, one of the world's oldest and
most prestigious medical journals. It is also the subject of a Comment
published online today.
"Dr. Rodger's
findings will benefit many women in many countries who will be spared from
hundreds of unnecessary and painful injections. They also underscore the
importance of conducting rigorous, well-designed clinical trials, something we
pride ourselves on at the Ottawa Hospital Research Institute," says Dr.
Duncan Stewart, chief executive officer and scientific director of the Ottawa
Hospital Research Institute, vice-president of research at The Ottawa Hospital
and professor of medicine at the University of Ottawa.
Dr. Rodger says he
hopes that doctors will stop prescribing LMWH to pregnant women with
thrombophilia and/or with previous pregnancy complications when it isn't
warranted. He also hopes the results of his study will cause some sober second
thought in the medical community and bolster the use of evidence-based
treatments.
"These findings
allow us to move on, to pursue other, potentially effective, methods for
treating pregnant women with thrombophilia and/or complications from placenta
blood clots," says Dr. Rodger.
There is still one
type of thrombophilia (anti-phospholipid antibodies) for which blood thinners
may be effective in preventing recurrent pregnancy loss. Also, some women are
advised to take low-dose aspirin while pregnant to help prevent pregnancy
complications. All women with thrombophilia need blood thinners to prevent
blood clots after delivery. As noted in the paper, some women with prior severe
pregnancy complications might still benefit from blood thinners, but this
requires further rigorous study. However, in all cases, pregnant women
experiencing any type of prior complication should consult their doctor about
the right course of treatment.
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