An interstitial gestation is an unusual type of pregnancy characterized by implantation of the embryo in the tubal portion that passes through the wall of the uterus. Therefore, it is an ectopic pregnancy since a large part of the gestational sac is located outside the uterus.
This type of ectopic pregnancy has a high morbidity and mortality rate. Its incidence is 2-4% of extrauterine gestations.