Menstrual cycle

The menstrual cycle is the recurring sequence of hormonal changes, usually every 21–35 days, that governs ovulation and prepares the uterine lining for a possible pregnancy. It has two main phases divided by ovulation: the follicular phase (egg development) and the luteal phase (post-ovulation), regulated by FSH, LH, oestradiol and progesterone. If pregnancy does not occur, the uterine lining sheds as a period, and the cycle restarts. Cycle length and regularity are important clues in a fertility evaluation, since irregular or absent cycles often point to anovulation, which is a common and treatable cause of infertility.

Also known as: monthly cycle, periods, menstrual period

Last reviewed: 9 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.