Ectopic pregnancy is a major health problem for women of childbearing age and a leading cause of pregnancy-related death in the first trimester. Untreated, ectopic pregnancy can lead to massive hemorrhage, infertility and death. With the advent of high-resolution transvaginal sonography, in conjunction with serum assays for the [beta]-subunit of human chorionic gonadotropin ([beta]-hCG), rapid and accurate diagnosis of this entity is now routinely possible.

Ectopic pregnancy is defined as implantation of a fertilized ovum outside the endometrial lining of the uterus. Based on data from the Centers for Disease Control and Prevention, ectopic pregnancy has an incidence of approximately 2% of all reported pregnancies and accounts for 9% of pregnancy-related deaths. (1)

First described in the 11th century, ectopic pregnancy was usually fatal. John Bard of New York City, NY, performed the first abdominal surgery for ectopic pregnancy in 1759. However, the survival rate for surgery was dismal in the 18th century and patients who were not treated surgically had a greater survival rate than those undergoing surgery. (2) With subsequent improvements in anesthesia, antibiotics and blood transfusion during the 20th century, mortality rates have significantly declined. Between 1970 and 1989 the risk of death from ectopic pregnancy dropped from 35.5 to 2.6 deaths per 10,000 cases despite a fourfold increase in incidence. (2)

Although ectopic pregnancy can occur in any woman capable of becoming pregnant, certain patient populations are more predisposed to ectopic pregnancy. Risk factors include: history of prior pelvic inflammatory disease, prior tubal surgery or ligation, presence of an intrauterine device, infertility treatment, history of prior ectopic pregnancy, and older age. Ectopic pregnancy has also been found to be more common in smokers than nonsmokers, possibly secondary to altered tubal motility. (3,4) These risk factors can be additive resulting in increased risk for women with multiple risk factors.

Ectopic pregnancy most commonly occurs in the fallopian tube with 90% to 95% occurring in the ampullary or isthmic portions (Figure 1). Less than 5% of ectopic pregnancies are interstitial in location. However, morbidity and mortality are higher for interstitial ectopic pregnancies due to later presentation and resultant massive hemorrhage. Cervical, ovarian and intra-abdominal ectopic pregnancies are rare and account for <1% of all ectopic pregnancies. (5) Ectopic pregnancies can also occur in the scar from a previous caesarean section. These ectopic pregnancies are also rare, accounting for <1% of ectopic pregnancies. They can present with vaginal bleeding as early as 5 to 6 weeks gestational age and as late as 16 weeks. These ectopic pregnancies, located in the anterior myometrium of the lower uterine segment, may rupture--resulting in severe hemorrhage and cardiovascular collapse. (6)

Clinically, the classic triad of signs/ symptoms of ectopic pregnancy consists of vaginal bleeding, abdominal or pelvic pain, and a tender adnexal mass. Unfortunately, this triad is only seen in about 50% of women presenting with ectopic pregnancy. (7) In many patients, presenting signs and symptoms are often nonspecific and can overlap with findings common to normal early-intrauterine pregnancies or miscarriages. They can...