Uterus (womb) 

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