Ovulation is the ejection of an egg – ovum – from a follicle on the ovary. It occurs, modally, approximately monthly in sexually mature females and is followed about two weeks later by menstruation unless pregnancy supervenes. A sensation commonly accompanying it, which may be related to the spilling of some fluid or blood into the peritoneal cavity is called mittelschmerz.
The fertile period in each cycle is around ovulation.
Ovulation is preceded by a gonadotrophin surge, which can be detected, followed by a hormonal rise produced by the luteal body and accompanied by a change in resting body temperature which may be measured.
The combined oral contraceptive pill prevents ovulation in most cycles.
Clomiphene in the early few days of the cycle, by blocking perception of oestrogen by the pituitary, causes an increased output of gonadotrophins. This increased drive to the ovary makes ovulation more likely and makes multiple ovulation more likely in those whose cycles are already ovulatory. This may have complications.
- The action of Clomiphene can be monitored by measuring progesterone on day 21 of the cycle.
- Counting ovarian follicles by ultrasound imaging can also be done.
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See also Delaying Menstruation