Do anticoagulants reduce the risk of recurrent miscarriage in pregnant women?

By Vladimir Tichelaar, Postdoc in TREC

B80647708About 12.5% of successful conceptions will end with an unexplained natural abortion within the first 12 weeks of pregnancy. However, in some women (1-5%) this happens more often or later in pregnancy. When a woman loses the fetus two or more times before 20 weeks of gestation, we call this recurrent miscarriage, and unexplained when uterine pathology, the antiphospholipid syndrome and chromosomal abnormalities are not found.

One explanation might be that the mother has a tendency of increased blood clotting. Most clotting tendencies are inherited but the antiphospholipid syndrome is acquired during life. If pregnant women with this disease are treated with aspirin and heparin, live birth rates increases from 40% to 75%. Therefore, these drugs are often prescribed to prevent unexplained recurrent miscarriage, in women with and without hereditary clotting disorders.

But does this really work? In 2010, Kaandorp and colleagues gave 364 women with unexplained recurrent miscarriage (most without a genetic clotting tendency) a fake treatment (placebo), or injections with anticoagulants or injections and aspirin. Unfortunately, the conclusion of the study is that there is no evidence that anticoagulants work (live births: placebo group 57%, aspirin group 51% and 55% in the anticoagulation group) (1).

Rodger and consorts recently investigated if women with inherited clotting tendencies would profit of anticoagulation to prevent pregnancy complications (2). They included 289 women and gave them no treatment or treatment with injected anticoagulation. However, no effect was observed (treated women had 8.2% and not treated women had 7.0% pregnancy loss).

These studies indicate that physicians should not recommend treatment with any anticoagulation to try to prevent recurrent pregnancy loss in women with such a history, independent of the presence of an inherited clotting disorder. An exception must be made for the acquired clotting disorder ‘the antiphospholipid syndrome.’

Reference:

  1. Kaandorp SP, Goddijn M, van der Post JA, et al. Aspirin plus heparin or aspirin alone in women with recurrent miscarriage. N Engl J Med 2010; 362: 1586-1596.
  2. Rodger MA, Hague WM, Kingdom J, et al. Antepartum dalteparin versus no antepartum dalteparin for the prevention of pregnancy complications in pregnant women with thrombophilia (TIPPS): a multinational open-label randomised trial. The Lancet 2014; 384: 1673-1683.
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