ECTOPIC PREGNANCY I—TUBAL PREGNANCY
Ectopic pregnancy refers to the implantation of the embryo in any place outside the uterine cavity. According to the site of implantation, four kinds of ectopic pregnancy are distinguished: tubal, ovarian, abdominal or peritoneal, and cervical. Between 10 and 15 of every 1000 pregnancies are ectopic, with the rate varying with age, race, and geographic location (highest in Jamaica and Vietnam).
Tubal pregnancy is by far the most frequent of all ectopic pregnancies. Here again, four types are recognized, depending on the portion of the tube in which the implantation takes place: interstitial (cornual), isthmic, ampullar, and infundibular. Although ampullar implantation has the highest incidence of tubal pregnancy, it is the interstitial form that is potentially the most serious from a clinical perspective.
The most important contributors to the occurrence and development of ectopic pregnancy are tubal damage or altered motility that causes the fertilized egg to be improperly transported, resulting in implantation outside the uterine cavity. The most common cause of tubal damage is a history of acute salpingitis (50%). In the majority of the remaining patients (50%), no risk factor is apparent. Abnormal embryonic development may play a role. Pelvic infections convey a sixfold increased risk; a prior ectopic pregnancy conveys a 10-fold increased risk, followed by prior female sterilization, increasing age (age 35 to 44, 3-fold greater rate than for women aged 15 to 24), nonwhite race (1.5-fold increased risk), assisted reproduction, cigarette smoking (30+/day, 3- to 5-fold increased risk), and endometriosis. Although intrauterine contraceptive devices (IUCDs) markedly decrease the risk of ectopic pregnancy compared with use of no method of contra- ception, if pregnancy occurs with an IUCD in utero, it is much more likely to be ectopic.
The early development of an ectopic pregnancy is the same as of an intrauterine gestation except for its location: the trophoblast possesses the same qualities and thus secretes chorionic gonadotropin, participating in the maintenance of the corpus luteum of pregnancy. This latter, in turn, elaborates enough estrogens and progesterone to induce all the maternal changes characteristic of the early stages of pregnancy. Initially, the level of excreted chorionic gonadotropin in the urine is the same as in a normally developing pregnancy. The mother may manifest decidual transformation of the endometrium and slight enlargement and softening of the uterus, just as in uterine pregnancy.
The possibility of ectopic implantation must always be kept in mind. A good clue is the history of amenorrhea of several weeks, followed by bleeding (usually spotting) accompanied by abdominal pain, which may be slight or intense. The subjective complaints of early pregnancy may be mild or nonexistent, as in normal pregnancy. Physical examination may reveal the presence of a tumor in the adnexa or some irregular, sometimes retrouterine, growth ﬁlling the cul-de-sac. Slight enlargement of the uterus, without cervical dilation but with tenderness in the posterior region of the cul-de- sac, may be present. Signs of hemorrhagic shock and peripheral collapse are seen when the intraperitoneal hemorrhage is severe, and in that stage the diagnosis, of course, becomes less and less problematic. Trans- vaginal ultrasonography may document no gestational sac within the endometrial cavity and an adnexal mass. The ﬁnding of free ﬂuid in the posterior cul-de-sac is common but not diagnostic. The ﬁnding of a fetal heartbeat in the adnexa is diagnostic.
Laboratory evaluations should include serial quantitativeβ-hCG levels (if patient’s condition permits). (Levels lower than 3000 mIU/mL are found in about half of cases.) Normal pregnancies should demonstrate a doubling of serum β-hCG levels every 48 hours, whereas abnormal pregnancies will not. Serum progesterone (low) may be of diagnostic help if pregnancy is <6 weeks’ gestation. Almost 90% of patients with an ectopic pregnancy have levels less than 30 nM/L (10 ng/mL). A hematocrit of less than 30 mL/dL is found in about one-fourth of women with ruptured ectopic pregnancy.