Incidence The most comprehensive data available on ectopic pregnancy rates were collected by the Centers for Disease Control and Prevention (CDC). The incidence of ectopic pregnancy increased significantly in the past century. In 1992, the latest year for which statistics are published, there were an estimated 108,800 ectopic pregnancies at a rate of 19.7 ectopic pregnancies per 1,000 reported pregnancies. This represents a sixfold increase compared with 1970 rates. The observed increase may represent an increase in detection and diagnosis resulting from more sensitive ultrasound technology, and a rise in sexually transmitted illnesses and assisted reproductive technologies (27). As Figure 20.2 demonstrates, while the absolute number of ectopic pregnancies continues to rise, the number of hospitalizations declined since the late 1980s, likely because of increasing outpatient management of this condition. Precise estimation of the true incidence of ectopic pregnancy is difficult, but the most recent estimate by the CDC is 2% of reported pregnancies (28). The data on demographic trends indicate that the highest rates occurred in women aged 35 to 44 years (27.2 per 1,000 reported pregnancies). When the data are analyzed by race, the risk for ectopic pregnancy among African Americans and other minorities (20.8 per 1,000) is 1.6 times greater than the risk among whites (13.4 per 1,000) (29). In 1992, 9% of all maternal deaths were attributable to ectopic pregnancy, down from 15% in 1988. The risk for death is higher for African Americans and other minorities than for whites. For all races, teenagers have the highest mortality rates, but the rate for African American and other minority teenagers is almost five times that of white teenagers (28,29). After an ectopic pregnancy, there is an 8% to 15% chance of recurrent ectopic pregnancy, with single-dose methotrexate conferring the lowest risk, while linear salpingostomy is associated with the highest risk (30). Many variables make accurate assessment of risk difficult (e.g., size and location of the ectopic pregnancy, status of the contralateral adnexa, treatment method, and history of infertility).
National hospital ambulatory medical care survey.
Figure 20.2 Estimation of the number of ectopic pregnancies (United States, 1970–1992).
(Adapted from MMWR 1995;44:46–48.) diethylstilbestrol (DES) exposure, and history of pelvic inﬂammatory disease (31,32). Intrauterine device (IUD) use and infertility are associated with increased risk for ectopic gestation, but these relationships are complex. Up to half of women with ectopic pregnancy will have no identifiable risk factors (33–35). Many other risk factors, including smoking and multiple lifetime sexual partners, are weakly associated with ectopic pregnancy (32).
Myoelectrical activity is responsible for propulsive activity in the fallopian tube (36). This activity facilitates movement of the sperm and ova toward each other and propels the zygote toward the uterine cavity. Estrogen increases smooth muscle activity, and progesterone decreases muscle tone. Aging results in progressive loss of myoelectrical activity along the fallopian tube, which may explain the increased incidence of tubal pregnancy in perimenopausal women (36). Hormonal control of the muscular activity in the fallopian tube may explain the increased incidence of tubal pregnancy associated with failures of the morning-after pill, minipill, progesterone-containing IUDs, and ovulation induction. There is no increase in the incidence of chromosomal abnormalities in ectopic pregnancies (37).