During puberty, females begin ovulating – the process of an egg cell (ovum) being released from the ovary. For a pregnancy to occur, the egg needs to meet with the sperm.

The eggs are released at different intervals, depending on each person’s menstrual cycle, during which the different hormones – estrogen, progesterone, luteinizing hormone (LH) and follicle-stimulating hormone – rise and fall. Ovulation happens whenever there is a rise in FSH and LH.

Generally, the entire cycle takes 28 days to complete, but for some people, it differs and can range from between 21–35 days. During ovulation, the egg makes its way down the fallopian tube and into the uterus. To get ready for a pregnancy, the hormones, estrogen and progesterone, cause the lining of the uterus to thicken. If a pregnancy doesn’t occur, the level of these hormones drops, which causes the thickened uterine lining to shed and tissue (blood, uterine wall, etc.) to be expelled. This shedding of this tissue is called menstruation or a period.