As the egg matures a cyst called a follicle develops on the ovary. This follicle may grow to about 2cm in diameter just before ovulation. It can be seen and measured on an ultrasound picture of the ovaries, and serial ultrasound pictures are another way of detecting ovulation. LH also stimulates the ovary to begin producing the second female hormone progesterone. Progesterone is only produced in significant amounts after ovulation has occurred and can be measured in the blood.
Progesterone changes the consistency of the vaginal mucus so that it becomes tacky or sticky.
This hormone also causes a slight increase in body temperature. Therefore ovulation may be detected by changes in the vaginal mucus, a small increase in body temperature or by changes in the amounts of oestrogen, LH and progesterone in the blood. The value of body termperature charts is limited because ovulation has already occurred by the time a temperature rise is recognized. Lack of Ovulation Ovulation usually occurs regularly once a month from puberty until the menopause apart from times of pregnancy and breast-feeding. In some women ovulation does not occur regularly or may not occur spontaneously at all.