The rate of ectopic pregnancies has been rising in the past decade and it is responsible for an increasing proportion of maternal deaths. A history of pelvic inflammatory disease is strongly associated with ectopic pregnancy. There is a higher rate of ectopic pregnancy among intrauterine device users than non-users. A history of abdominal surgery has been associated with ectopic pregnancy and there is some evidence that women taking certain hormonal preparations experience excess ectopic pregnancies. Through a critical review of the literature, the author explores the evidence for these associations. The paper closes with recommendations for future research.
PIP: This review of the literature concerning the rising rate of ectopic pregnancies in the past decade focuses on the following: maternal characteristics; causal factors (pelvic inflammatory disease); relationship to hormonal preparations; previous surgery; and repeat ectopic pregnancy. Ectopic pregnancy is defined as implantation of the blastocyst anywhere other than the endometrial lining of the uterus. Over 95% of such pregnancies involve the fallopian tube, but the term includes implantations in the uterine cornu, cervix, ovary and abdominal cavity. Ectopic pregnancy is a major factor in maternal mortality. There is an estimated case mortality rate of 2-4/1000. Approximately 6-10% of maternal deaths are attributed to ectopic pregnancy. The reported incidence of extrauterine pregnancy varies widely, but almost all authors are in agreement that there has been a noticeable increase in the 1970s, with virtually a doubling in incidence. In general, the women who develop ectopic pregnancies tend to be in their late 20s and older. Tubal pregnancy has traditionally been attributed to scarred fallopian tubes and has been associated with infertility or low parity. Researchers who have examined race in relation to ectopic pregnancy have found a greater incidence among nonwhites than whites, ranging from 1.5-4 times the incidence. Pelvic inflammatory disease (PID) is classically believed to be the primary cause of ectopic pregnancy. Resolution of the inflammatory process with fibrous tissue ultimately leads to distortion of the fallopian tubes with consequent impeded passage of the ovum, which finally results in diminished fertility and/or tubal pregnancy. Many studies demonstrate an increased proportion of ectopic pregnancy among IUD users. Various authors have reported an excess number of ectopic pregnancies among the unplanned pregnancies occurring to women using progestin only oral contraceptives with estimates ranging from a 2-5 fold increase. Surgical sterilization of the female blocks transport of the ovum down the fallopian tubes by ligating, transecting, coagulating or occluding them, and if such an obstruction were to be incomplete, it would predispose the woman to a tubal pregnancy. The fact that ectopic pregnancy is due, at least in some instances, to some chronic impairment of the reproductive function is demonstrated by the high incidence of recurrence among women experiencing extrauterine pregnancies and their poor future reproductive outcomes. Many of the studies suffer from methodological flaws, but when 10 studies, whatever the inadequacies of their designs, show the same finding, it is at least a strong hint that the observed relationships are real.