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extrauterine pregnancy[¦ek·trə′yüd·ə‚rēn ′preg·nən·sē]
(ectopic pregnancy), development of the human fetus outside the uterus. Depending on the site of attachment (implantation) of the ovum, extrauterine pregnancy may be tubal, ovarian, or abdominal. The tubal form is the most common, occurring in 99 percent of cases of extrauterine pregnancy. The ovum is fertilized by a spermatozoon in the Fallopian tube. Extrauterine pregnancy occurs when the ovum is unable to move through the tube to the uterus. This usually happens when the mucous membrane of the tube is injured as a result of previous inflammatory diseases of the internal genitalia (one-third of all extrauterine pregnancies), after abortions, or after gonorrhea. In some cases extrauterine pregnancy develops in the presence of glandular formations in the uterine musculature (adenomyosis) or because of underdevelopment (infantilism) of the genitalia caused by a hormonal deficiency. In other cases extrauterine pregnancy may occur as a result of the so-called external movement of the ovum, during which the fertilized ovum from the ovary on one side enters the uterine tube on the other side. By the time the ovum enters the tube a trophoblast is already developing, and the ovum is able to become implanted in the mucous membrane.
An extrauterine pregnancy is generally interrupted between the fourth and sixth weeks because of destruction of the tubal wall by the villi of the ovum (rupture of the tube) or, if the ovum became attached close to the abdominal end of the tube, because of the ejection of the ovum (caused by contractions of the tube) into the abdominal cavity—tubal abortion. The interruption of an extrauterine pregnancy by rupture of the tube results in internal bleeding and shock due to sudden acute pain in the lower abdomen. Intra-abdominal bleeding is less in a tubal abortion. The gripping pains, accompanied by brief fainting, disappear in a few hours, and the patient may feel well. However, the danger of repeated, severe internal bleeding remains, and therefore additional examinations are often needed to determine an extrauterine pregnancy, such as a pregnancy test and puncture of the posterior fornix vaginae, with the patient kept under observation sometimes for two to three weeks. In rare cases, after a tubal abortion the ovum becomes attached in the abdominal cavity (secondary abdominal pregnancy) and develops until a late stage. By performing a laparotomy it is sometimes possible to deliver a live, mature infant. Treatment involves surgical removal of the damaged Fallopian tube. Every woman who has undergone surgery for an extrauterine pregnancy should be treated for some time thereafter to prevent a secondary extrauterine pregnancy in the other tube.
REFERENCESAleksandrov, M. S., and L. F. Shinkareva. Vnematochnaia beremennost’. Moscow, 1961.
Persianinov, L. S. “Vnematochnaia beremennost’.” In Mnogotomnoe rukovodstvo po akusherstvu iginekologii, vol. 3, book 1, 1964.
V. A. POKROVSKII