An ectopic pregnancy is a pregnancy that occurs outside the uterus (womb) – in the Fallopian tube or elsewhere. The embryo cannot develop normally and spontaneous abortion often occurs. If not, urgent surgery is necessary to save the mother from serious, possible fatal hemorrhage.
Referring to the diagram at right, an ectopic (or extrauterine) pregnancy occurs when the egg released from the ovary (1) and fertilized by sperm (2) in the Fallopian tube (3) fails to passed down into the top of the uterus (4), where it would normally implant in the wall of the uterus. If the zygote does implant in the wall in the wall of the Fallopian tube (6), there is not the space or the blood supply to nurture a fetus to full term.