Ovulation is the term used for the release of a viable egg from the ovary.
Conception can not occur until the viable egg is released, and starts its journey down the fallopian tube towards the uterus.
The trigger for ovulation to occur is a sudden increase in the blood levels of the hormone LH, released from the pituitary gland. Normally the egg is released 14 days before the 1st day of the next menstrual period is due to occur. If conception and implantation occurs the period does not occur and an early pregnancy is progressing.
It is possible to measure LH in urine using ovulation prediction tests
LH levels in blood can also be tested by hospital tests, normally on day 19 of the cycle.