Oocyte abnormalities

The main cause of female infertility due to oocyte abnormalities is a failure to ovulate regularly or, in some cases, at all. Those disorders that result in oligo-ovulation or anovulation are also causes of amenorrhea (see Chapters 30 and 31), and fall into three categories: hypothalamic dysfunction, pituitary disease and ovarian dysfunction.

Common hypothalamic causes of anovulation include abnormalities of weight and body composition, strenuous exercise, stress and travel. Pituitary or endocrine disorders associated with anovulation are hyperprolactinemia and hypothyroidism. The two most common known causes of ovarian dysfunction are polycystic ovary syndrome and premature ovarian failure. Oocyte abnormalities more complex than simple anovulation cause the fairly rapid decline in fertility that occurs as women enter their 40s.

Female anatomic abnormalities

Fallopian tubal disease is usually the result of inflammatory scarring of the fallopian tubes. This may be caused by pelvic inflammatory disease, appendicitis with rupture, septic abortion, previous surgery and, occasionally, previous use of an intrauterine device. The most common site of tubal blockage is the distal fimbriated end of the tube. These blockages are typically associated with additional pelvic adhesions and may affect up to 20% of the women in infertile couples. Purposeful, surgically-induced blockage occurs with surgical sterilization; some women regret their contraceptive decision post-tubal sterilization and present to the fertility specialist requesting reversal.

Endometriosis is a common disorder, characterized by the presence of tissue resembling endometrium outside of its normal position lining the uterus. The glands and stroma of endometriosis are usually responsive to gonadal hormones and the biochemical changes the steroids induce in this ectopic endometrium mimic those seen in endometrium within the uterine cavity. Increased prostaglandin production by perimenstrual and menstrual endometriotic lesions is thought to promote the inflammation, fibrosis and adhesion formation characteristic of the disorder. Endometriosis lesions can be found almost anywhere in the pelvis but are most common on the peritoneal surfaces covering the pouch of Douglas, bladder, ovaries, fallopian tubes, bowel and appendix. Women with endometriosis can present with pelvic pain, adnexal masses (endometriomas), infertility, or any combination of these.

Uterine leiomyomas, also known as fibroids or uterine myomas, are benign smooth muscle tumors of the uterus. They are the most common pelvic tumor in women, and may be located anywhere within the wall of the uterus or may hang from a stalk containing the blood supply to the tumour (pedunculated leiomyomas). Pedunculated leiomyomas may hang from the outside of the uterus or may project into the endometrial cavity. Those leiomyomas that distort the uterine cavity (submucosal in location) or physically obstruct fallopian tubes are most closely associated with decreased fecundity.