Among 10,685 women studied, the risk of ectopic pregnancy within 10 years after sterilization was about 7 per 1,000 procedures. The likelihood of an ectopic pregnancy varied according to the method of sterilization and the age at which the women underwent the sterilization procedures.

Ectopic pregnancy, also known as a tubal pregnancy, is a potentially life-threatening form of pregnancy in which implantation of the fertilized egg occurs outside the uterus.
 

These findings are reported in "The Risk of Ectopic Pregnancy After Tubal Sterilization" by Herbert Peterson, Zhisen Xia, Joyce Hughes, Lynne Wilcox, Lisa Tylor, and James Trussell for the U.S. Collaborative Review of Sterilization Working Group in the March 13, 1997 issue (336:762-767) of The New England Journal of Medicine.*
 
The purpose of this 14-year study, which was supported by the National Institute of Child Health and Human Development at the National Institutes of Health, was to assess the risk of ectopic pregnancy in women who have undergone tubal sterilization.
 
Ectopic pregnancy may occur long after sterilization. Ectopic pregnancy after tubal sterilization is not rare, particularly among women sterilized before age 30.
   
Those who provide care to women of childbearing age should not assume that a history of tubal sterilization rules out the possibility of an ectopic pregnancy in a woman who has symptoms or signs of pregnancy, especially ectopic pregnancy.
   
The study also found that the likelihood of an ectopic pregnancy varied according to the method of sterilization and the age at which the women underwent the sterilization procedure. Women who were under age 30 at the time of the procedure were twice as likely to have a subsequent ectopic pregnancy as older women. Further, the researchers found that ectopic pregnancy may occur many years after tubal sterilization.
 
Tubal sterilization is an increasingly common method of contraception in the United States, and even though pregnancy after sterilization is uncommon, it can occur, and it may be ectopic.
 
Women who think that they might be pregnant after sterilization should check with their health care providers, even if the sterilization was performed many years earlier.
 
Approximately 100,000 ectopic pregnancies occur each year, and relatively few are caused by sterilization. Often the actual cause is unknown, but many cases result from tubal damage incurred from sexually transmitted infections.

Ectopic pregnancies are the leading cause of pregnancy-related deaths in the first trimester and account for 9% of all pregnancy-related deaths in this country.

[CDC Reproductive Health Information Source, 7/04 http://www.cdc.gov/reproductivehealth/mh_ectopic.htm]