Allergy to heparin. Special problems set by pregnant women.

Oral anti-coagulants are always contra-indicated for pregnant women. Only anti-coagulants of the types of heparin or its derivatives may be used. However, some patients have an allergy to heparin. In this article the correct action to make both for diagnosis and prevention is studied. We present 2 observations of heparin-allergic pregnant women with, in the first case an attempted tolerization which failed and in the second case there was success in a second pregnancy with low-molecular weight heparin.