ECTOPIC PREGNANCY III— INTERSTITIAL, ABDOMINAL, OVARIAN
When, during the process of abortion or rupture, the trophoblast, after total separation, implants itself again somewhere in the peritoneum, as happens on rare occasions, it may grow and develop into a secondary abdominal pregnancy. The embryo in such cases may have remained in its original amniotic sac, or a new sac may have formed from the surrounding tissues. A secondary abdominal pregnancy may also result from a beginning tubal implantation that ruptured and became inserted between the leaves of the broad ligament. If the latter should rupture again, the embryo in the fetal sac may extrude into the peritoneal cavity, with the placenta remaining in the extraperitoneal position between the broad ligament sheets. In still more exceptional cases, the fertilized ovum may escape through the open end of the tube, attaching itself to the parietal or visceral peritoneum or the omentum, developing into a primary abdominal pregnancy. It has even been reported that an abdominal pregnancy has originated from a defect in the uterine wall, which had been ﬁlled and closed up by the omentum during the healing period after cesarean section. The remarkable feature of these abdominal pregnancies is that they may continue to near term before an occasion for diagnosis may even arise, even in the face of repeated ultrasonographic studies. The incidence of abdominal pregnancy is estimated to be roughly 1 in 10,000 live births.
Fetal salvage in these cases is the exception, though survival rates of more than 50% have been reported if the pregnancy progresses beyond 30 weeks’ gestation. When survival does occur, there is a much increased rate of fetal malformations, including facial or cranial asymmetry, limb defects, and central nervous system anomalies. Delivery must be by laparotomy, but such surgeries are associated with massive hemorrhage even when care is taken not to disturb the placenta.
Ovarian pregnancy is the rarest form of ectopic pregnancy. Although full-term ovarian pregnancies are on record, they more often eventuate in encapsulation and degeneration of the fetal mass. The diagnosis can be made only by ﬁnding ovarian structures around the amniotic sac upon microscopic study of the removed ovary. In a primary ovarian pregnancy, the oviduct and the broad ligament should not be involved.
In a low percentage of tubal implantations, the fertilized ovum may settle in the uterine end of the tube its intramural or interstitial segment. In an interstitial pregnancy, owing to the greater muscular mass and vascularity, fetal growth may continue longer without rupture than in other types of tubal pregnancy. The danger resulting from rupture, however, is also greater, because the hemorrhage may be so profuse that it is fatal within a very short time. Furthermore, the diagnosis of ectopic gestation in cases of interstitial pregnancies is more difﬁcult in view of the lack of a mass in the tube by palpation or ultrasonography and an asymmetric uterine enlargement, which may be interpreted as a seemingly normal pregnancy.
Cervical pregnancy (not illustrated) has been observed in only a few cases. The cervical endothelium, not undergoing the typical progestational changes, is not adequately prepared to receive the trophoblast or permit nidation. The placenta is attached to the cervical myometrium, and gestation advances not longer than into the third month, when abortion occurs. Some authors do not classify this condition with the ectopic pregnancies, but one should bear in mind that it shares with these anomalies all the dangers connected with the difﬁculty of removing the placenta without serious hemorrhage. The low contractility of this portion of the uterus and the proximity of the uterine vascular supply increase the risk of hemorrhage even during curettage.