Ovulation occurs when a mature egg is released from a woman’s ovary. It occurs midway through her normal menstrual cycle, usually between day 12 and day 16. The point at which ovulation occurs is determined by hormone levels in the body, but ovulation is defined as the rupture of a mature ovarian follicle, which allows an egg to start moving into and down the fallopian tube.
If you are having problems with infertility, the first step that you can take is to monitor your pattern of ovulation. There is a wide variation in the day of ovulation in some women, and this will show as irregular periods. The time of your next period always occurs 12–16 days after ovulation, unless you become pregnant.
Ovulation can be tracked by taking your body temperature each day; ovulation causes a slight rise in temperature for 2–3 days. You can also check the consistency of your vaginal mucus. This becomes much thinner and more liquid around the time of ovulation.
When trying to get pregnant, you should aim to have regular sexual intercourse around the time of ovulation; the peak chance of pregnancy is around 40 hours later, so there will be 3–5 days in your cycle when sex should take place.
If you continue to have problems with your fertility, you may then have more intensive tests to look at how you are ovulating. Blood tests can monitor the hormone levels that reveal exactly when ovulation occurs. In the first part of your cycle, your pituitary gland produces follicle stimulating hormone (FSH), which stimulates one of the follicles in the ovary to develop into a mature egg. Another hormone, luteinising hormone (LSH) is released as a surge half way through your menstrual cycle and acts as the trigger for ovulation. This surge can be detected by your blood tests.
If your egg is fertilised after you have ovulated, the follicle that released the egg continues to develop into a structure called the corpus luteum. This produces progesterone to nurture the pregnancy until the embryo implants in the wall of the uterus, and hormones produced by the placenta take over.