By these terms is meant the development of the foetus in any other situation than the normal one in the uterus.
The causation is somewhat obscure, but if we accept the views of Lawson Tait it usually results from disease of the Fallopian tubes, which by destroying the ciliated epithelium allows the spermatozoa to pass up the tube and impregnate the ovum before it reaches the uterus.
According to this author normal impregnation always occurs in the uterus, as the ciliated epithelium of the tubes prevents the ascent of the spermatozoa. If thi; ciliated epithelium be destroyed the spermatozoa may pass up as far as the ovary.
According to the position in which the impregnated ovum settles various forms have been distinguished, namely, Tubal, Tubo-ovarian, Ovarian, and Abdominal. The existence of an [abdominal pregnancy, except by rupture of a tubal one, is denied by recent authorities (Mayr hofer, LaWson Tait), and even ovarian pregnancy, if it occurs, is very rare. Undoubtedly tubal pregnancy is by far the commonest. An excessively rare ectopic pregnancy is that in which, from existing perforation of the uterus (as from a previous Caesarian section), the ovum has escaped into the abdominal cavity.
Tubal pregnancy occurs either in the free part of the tube or in the part surrounded by the uterine tissue. In the latter case the form is called Interstitial pregnancy.
If an impregnated ovum settle in the tube, the placenta, as it forms, adheres to the wall of the tube and forms vascular connections. As the tube does not, like the uterus, enlarge under the stimulus of pregnancy, the growing ovum thins its wall, and rupture occurs (primary rupture). This always takes place before the fourteenth week. The rupture may be into the peritoneal cavity or into the broad ligament. At the time of rupture there is haemorrhage, which in the case of rupture into the peritoneum is usually fatal.
As a result of this primary rupture the foetus usually dies, and in that case the conditions are those of the Pelvic hematocele, intraperitoneal or extraperitoneal. In either case there may be subsequent encapsuling or absorption of the dead foetus (which will be very small) or there may ensue a suppuration of the hematocele.
The foetus may survive and the placenta may acquire fresh connections, so as to allow of the completion of the full term of utero-gestation. Before this, however, especially when the foetus is in the broad ligament, there may be a secondary rupture, resulting in some cases in a fatal haemorrhage, but in others merely in a fresh adhesion inside the peritoneum.
If the full term be reached the foetus dies, and, unless removed by operation, remains as a foreign body. As a rule general peritonitis results, sometimes with the ultimate formation of an abscess. If the death of the mother does not occur soon the abscess may come to the surface and the foetus may bo discharged piece-meal.
In some rare cases the foetus gives rise to no active inflammation, and after its death remains quiescent. The foetus, then, through time acquires the characters which have given rise to the designation Lithopffidion.
It becomes surrounded by a connective tissue capsule, inside which the mummified foetus may remain for many years. The capsule usually becomes infiltrated with lime salts, so that a kind of shell is formed around the foetus. The foetus itself may be partly calcified, but its soft structures are often little altered or may be converted into adipocere. Cases are on record of a duration of life extending as long as fifty years after an ectopic pregnancy, and in some cases normal pregnancies have occurred in the interval.
Cases have been observed of molar extra-uterine pregnancy.
Mayrhofer, Billroth's Handb. d. Frauenkrankh., i.; Lawson Tait, Ectopic pregnancy, 1888 (gives full account and collection of cases of Lithopaedion); Virchow, Wiirzb. Verhandl., i.; Sappey, Comptes Eendus, Aug. 27, 1883.