Biology of nidation and ectopic implantation.

The incidence of ectopic pregnancy has been steadily growing during the past decade; this fact can only partially be related to known factors (PID, use of IUDs, minipill, inductors of ovulation, sterilization reversal). Ectopic pregnancy is still a frequently misdiagnosed pathology; nevertheless, the recent advances in early diagnosis have allowed a decrease in the mortality rate and an improvement in subsequent fertility. In absence of obvious tubal abnormalities it is difficult to assess the cause of an ectopic implantation.