Warfarin has a stronger effect on some people than on others. This test will tell your doctor how well the warfarin is working. Some other medicines can make warfarin more or less strong. Ask your doctor before you take a new medicine, even nonprescription medicines and vitamins. If you're pregnant, you shouldn't take warfarin.
Warfarin can cause birth defects.
Instead, you must use heparin until you have your baby. If you want to get pregnant and you're already taking warfarin, talk with your doctor about changing to heparin. Sexually active women who take warfarin should use birth control. This handout provides a general overview on this topic and may not apply to everyone. To find out if this handout applies to you and to get more information on this subject, talk to your family doctor.