The most common location for the fertilization of the egg is the fallopian tube. The zygote then undergoes several divisions and some development before implanting in the endometrium of the uterus as a blastocyst. Abnormal implantation can occur while the blastocyst is still in the fallopian tube, resulting in an ectopic pregnancy. This event generally requires surgery to rectify and can be extremely dangerous to the mother and developing embryo.