A woman's ovaries do not alternate every month to release an egg during ovulation, according to BabyCenter. One of a woman's two ovaries randomly releases an egg during ovulation.
Women who have gone through puberty and have yet to reach menopause ovulate each month, according to BabyCenter. The process of ovulation occurs when one or more eggs is released from a woman's ovaries between her periods. For a woman to become pregnant, the egg that is released during ovulation must come in contact with a man's sperm. If this occurs, then the sperm can fertilize the egg, and the fertilized zygote may implant itself in the woman's uterus.