The most common male infertility factors include azoospermia (no sperm cells are produced) and oligospermia (few sperm cells are produced). Sometime, sperm cells are malformed or they die before they can reach the egg. In rare cases, infertility in men is caused by a genetic disease such as cystic fibrosis or a chromosomal abnormality.
The most common female infertility factor is an ovulation disorder. Other causes of female infertility include blocked fallopian tubes, which can occur when a woman has had pelvic inflammatory disease or endometriosis. Congenital anomalies (birth defects) involving structure of the uterus and uterine fibroids are associated with repeated miscarriages.