An ectopic pregnancy occurs when baby starts to develop outside the womb (uterus). The most common site for an ectopic pregnancy is within a fallopian tube. However, in rare cases, ectopic pregnancies can occur in the ovary, the stomach area, and the cervix. An ectopic pregnancy is usually caused by a condition that blocks of slows the movement of a fertilized egg through the fallopian tube to the uterus. This may be caused by a physical blockage in the tube. Most cases are a result of scarring caused by a past infection in the fallopian tubes, surgery of the fallopian tubes, or a previous ectopic pregnancy. Up to 50% of women who have ectopic pregnancies have had inflammation of the fallopian tubes (salpingitis) or pelvic inflammatory disease (PID). Some ectopic pregnancies can be due to birth defects of the fallopian tubes, endometriosis, complications of a ruptured appendix, or scarring caused by previous pelvic surgery. In a few cases, the cause is unknown. Sometimes, a woman will become pregnant after having her tubes tied (tubal sterilization). The risk of an ectopic pregnancy due to this procedure may reach 60%. Women who have had successful surgery to reverse tubal sterilization in order to become pregnant also have an increased risk of ectopic pregnancy. Taking hormones, specifically estrogen and progesterone (such as those in birth control pills), can slow the normal movement of the fertilized egg through the tubes and lead to ectopic pregnancy. Women who have in vitro fertilization or who have an intrauterine device (IUD) using progesterone also have an increased risk of ectopic pregnancy. The "morning after pill" (emergency contraception) has been linked to some cases of ectopic pregnancy. Ectopic pregnancies occur from 1 in every 40 to 1 in every 100 pregnancies.
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