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.
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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.
