The oocyte is released from the ovary and enters the end of the fallopian tube furthest from the uterus known as the fimbriated end.
Fertilization takes place in the fallopian tube close to the ovary.
As the embryo develops within the first week, it traverses the fallopian tube where it will eventually implant into the wall of the uterus. This process occurs in greater than ninety-eight percent of pregnancies. An ectopic pregnancy, or tubal pregnancy, occurs when implantation of the embryo occurs anywhere outside of the uterus. Another type of ectopic pregnancy which may occur is known as a heterotopic ectopic pregnancy and this refers to an ectopic which coexists with an intrauterine pregnancy. The past two decades in the United States has seen a marked increase in the number of ectopic pregnancies.