Under normal circumstances, women ovulate only one mature egg a month, alternating between the two ovaries. Only in rare cases does she ovulate more than one egg or no ovulation occurs. The follicles are stimulated by follicle-stimulating hormone and start to grow and develop. As each follicle develops at a different rate, the secretion of follicle-stimulating hormone stops when one of the follicles matures, leaving no possibility for the other follicles to continue to develop. A woman’s ovulation period is usually about 14 days before her next period. Having intercourse around 1-2 days before and after ovulation will increase the chances of pregnancy. However, some women are affected by environmental changes and mood swings, which can cause ovulation to occur earlier or later, or they may ovulate 2 eggs in a month, or even not at all. Women who are expecting can have an ultrasound examination in the middle of their menstrual period to check the development of their follicles so that they can arrange intercourse in time to increase their chances of conception.