Ectopic pregnancy

Definition

An ectopic pregnancy is an abnormal pregnancy that occurs outside the womb (uterus). The baby cannot survive.

Alternative Names

Causes

An ectopic pregnancy occurs when the baby starts to develop outside the womb (uterus). The most common site for an ectopic pregnancy is within one of the tubes through which the egg passes from the ovary to the uterus (fallopian tube). However, in rare cases, ectopic pregnancies can occur in the ovary, stomach area, or cervix.

An ectopic pregnancy is usually caused by a condition that blocks or 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:

• Past ectopic pregnancy
• Past infection in the fallopian tubes
• Surgery of the fallopian tubes

Up to 50% of women who have ectopic pregnancies have had swelling (inflammation) of the fallopian tubes (salpingitis) or pelvic inflammatory disease (PID).

Some ectopic pregnancies can be due to:

• Birth defects of the fallopian tubes
• Complications of a ruptured appendix
• Endometriosis
• 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). Ectopic pregnancies are more likely to occur 2 or more years after the procedure, rather than right after it. In the first year after sterilization, only about 6% of pregnancies will be ectopic, but most pregnancies that occur 2-3 years after tubal sterilization will be ectopic.

Women who have had surgery to reverse tubal sterilization in order to become pregnant also have an increased risk of ectopic pregnancy.

Taking hormones, especially 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 in 1 in every 40 to 1 in every 100 pregnancies.

References

Jian Z, Linan C. Ectopic gestation following emergency contraception with levonorgestrel. Eur J Contracept Reprod Health Care. 2003 Dec;8(4):225-8.

Sheffer-Mimouni G, Pauzner D, Maslovitch S, Lessing JB, Gamzu R. Contraception. 2003 Apr;67(4):267-9.

Nielsen CL, Miller L. Ectopic gestation following emergency contraceptive pill administration. Contraception. 2000 Nov;62(5):275-6.

Furlong LA. Ectopic pregnancy risk when contraception fails. A review. J Reprod Med. 2002 Nov;47(11):881-5. Review.

Katz VL, Lentz GM, Lobo RA, Gershenson DM. Katz: Comprehensive Gynecology. 5th ed. Philadelphia, Pa: Mosby;2007.