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Clotting Disorders
April 2002

Q. I am a 22-year-old female. I have 2 genetic clotting disorders, Factor V and a Prothrombin mutation. I have been on coumadin since I was 19-years-old after finding several clots in my left leg. I have been told I must stay on anticoagulants for life. For obvious reasons I stopped taking the ortho novum I was on to prevent pregnancy. I know that coumadin does cause birth defects.

My long-term partner and I now use condoms. However, there have been a few times when I've faced the concern that I might be pregnant. I am concerned about the effects of coumadin during the first month when I may not realize I am pregnant. My doctor doesn't recommend switching me to heparin unless I am planning to have a child.

Has there been any progress in finding an anticoagulation method other than heparin that doesn't cause birth defects? Or a birth control method as reliable as the pill that doesn't cause clotting problems in those of us unfortunate enough to have the disorders I do? I am kind of in a catch 22. Also if I do become pregnant and switch to heparin after the first month what are the chances of risk to the unborn child?

A. These are indeed complicated issues; coumadin is required for your own safety yet poses a risk to the fetus if you become pregnant. Most evidence indicates the coumadin risk occurs between the 6th and 12th week of pregnancy, so if a pregnancy occurred and was known early, this critical time period could be avoided and the switch made from coumadin to heparin. The heparin has been studied extensively and does not seem to pose any risk of birth defects. Unlike coumadin, the heparin does not cross over the placental barrier to the fetus.

Concerning birth control methods, the estrogen component of the pill is associated with clotting. Ask your doctor whether the progesterone-only methods (minipill or injection) might be safe for contraception in your case.

Medical references (available through a hospital or medical school library):

  1. Bazzan M, Donvito V. Low-molecular-weight heparin during pregnancy. Thromb Res. 2001 Jan 1;101(1):V175-86. Review.
  2. Ginsberg JS, Greer I, Hirsh J. Use of antithrombotic agents during pregnancy. Chest. 2001 Jan;119(1 Suppl):122S-131S. Review.
  3. Federman DG, Kirsner RS. An update on hypercoagulable disorders. Arch Intern Med. 2001 Apr 23;161(8):1051-6.
  4. Barbour LA. ACOG practice bulletin. Thrombembolism in pregnancy. Int J Gynaecol Obstet. 2001 Nov;75(2):203-12. No abstract available.

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