Studies have found a relationship between women who have obstructive sleep apnoea and smaller babies. The reason for this lies in the fact that sleep apnoea causes an obstruction of oxygen, which in turn means less oxygen reaches the baby. Though women who snore should not panic, as further research is needed to give more credence to this case of causation.

An older woman's eggs aren't fertilized as easily as a younger woman's eggs — and might not develop normally even after fertilization occurs.

A severely underweight woman (with less than 17 percent body fat) may have irregular ovulation, reducing their odds of conception.

Chlamydia and gonorrhea are important preventable causes of pelvic inflammatory disease (PID) and infertility.

These include the testes, where sperm is made, several ducts (tubes) where sperm is stored, and the penis. The penis has a single duct called the urethra; this releases both sperm and urine. Also included in the male reproductive system are the accessory sex glands, which include the prostate gland and seminal vesicles.

Sufficient follicle stimulating hormone action is also needed for proper sperm production.