After the sperm has fertilized the egg in the fallopian tube, the resulting embryo travels to the uterus to implant and develop.
Implantation may not occur because;
- The uterus is not receptive because of infection or inflammation (eg. STDs, endometriosis)
- The uterus is not receptive because of an abnormal anatomy (eg. fibroids or polyps)
- The uterus has been surgically removed
- The uterus did not form during fetal development