Vaginal bleeding during the first trimester (12 weeks) occurs in many women. This does not necessarily mean that a miscarriage is immanent; however, any vaginal bleeding during pregnancy should be investigated by your health care provider. Most miscarriages occur during the first 12 weeks of pregnancy. About half of pregnant women who experience vaginal bleeding during the first 12 weeks of pregnancy do not have a miscarriage. If you pass anything you think is fetal tissue be sure to take it to your health care provider for examination.
Unfortunately, most miscarriages are not preventable; a miscarriage is often nature's way of dealing with abnormalities. Exercise and sex have not been proven to cause miscarriage, in fact continuing regular exercise (always check with your health care provider before starting an exercise program during pregnancy) during pregnancy can help ease labor when it is time for your new baby to be born. Fifteen to twenty percent of all pregnancies end in miscarriage.
Another potential cause of bleeding during early pregnancy is having an ectopic pregnancy. An ectopic pregnancy occurs when the fertilized egg implants itself in one of the fallopian tubes. This is often called a "tubal pregnancy." Ectopic pregnancy is much less common than miscarriage occurring in about one out of sixty pregnancies.