An ectopic or extrauterine pregnancy is one in which the blastocyst implants anywhere other than the endome-trial lining of the uterine cavity. As shown in Figure 13.1, 98% of ectopic pregnancies implant in the fallopian tube, with 80% occurring in the ampullary segment. Other locations include, but are not limited to, the ovary, cervix, and abdomen. In some form, they account for 1.3% to 2% of reported pregnancies in the United States.
In the past, ectopic pregnancy was life-threatening. Earlier diagnosis made possible by the new ability to detect the β-subunit of human chorionic gonadotropin (hCG), combined with high-resolution transvaginal sonography (TVS), has reduced this threat. Nevertheless, ectopic pregnancies remain an important cause of morbidity and mortality in the United States. The incidence of ectopic pregnancy has increased consistent with the rise in chla-mydial infections.
Without intervention, the natural course of a tubal preg-nancy can lead to tubal abortion, tubal rupture, or sponta-neous resolution. Tubal abortion is the expulsion of products of conception through the fimbriated end. Thistissue can then either regress or reimplant in the abdomi-nal cavity. Tubal rupture is associated with significant intra-abdominal hemorrhage, often necessitating surgical intervention.