Ovulation is a normal and expected part of the female reproductive cycle.  It occurs roughly in the middle of a menstrual cycle and is the time when the egg is released for fertilization.  It is considered the time a woman is most fertile during her cycle.

Many things have to come into play before ovulation can occur.  First the woman must menstruate, ridding the body of the outer layer of the endometrium of the uterus.  The estrogen level of the body begins to rise, thickening the lining of the uterus and readying it for ovulation and the ultimate acceptance of the fertilized embryo.  During this time, the egg is maturing, and often multiple eggs mature at the same time.

At around day thirteen the body’s level of follicle stimulating hormone and luteinizing hormone, two hormones that come from the pituitary, begin to surge and cause one or perhaps two or more of the egg sacs to ripen and release the egg. This is the moment of ovulation.

The follicle stimulating hormone and luteinizing hormone go way back down and progesterone, coming from the corpus luteum, which is the empty egg sac that has now become very important to the maintenance of the uterine lining and any pregnancy that develops. 

The uterine lining goes from being proliferative, meaning it is increasing in size and volume, to a secretory endometrium, ripe for implantation of a possible pregnancy.  Both the progesterone and the estrogen drop way down just prior to a woman getting her period again or remain up if a pregnancy has happened.

Ovulation generally occurs on day 14 of a 28 day cycle but there are some women who have cycles much longer than 28 days, which makes it more difficult to determine the date of ovulation.  In such cases, it is the last portion of the menstrual cycle, or the secretory phase, which remains relatively stable at about 14 days so that ovulation is calculated backwards, and is fourteen days before the expected period.

Women often want to know when they are able to get pregnant, or the moment of ovulation.  It can be determined by checking what’s known as the basal body temperature.  Progesterone, which begins to be released at the time of ovulation, raises the body temperature by a half a degree. 

When a woman checks her temperature using a basal body temperature thermometer, she checks her temperature first thing in the morning, before getting out of bed.  The temperature drops by a fourth of a degree or so at the time of ovulation in some cases and then it rises by a half degree above baseline.  This means that ovulation has occurred.

Another way to detect ovulation is to use an ovulation test kit, which detects the LH surge occurring 24-36 hours before the expected ovulation.  Women can buy these test kits which will detect the two or so more fertile days of the cycle and determine when ovulation is about to occur.  Test kits cost $30 to $50 dollars a kit and are good for a single cycle.  They are especially useful in situations when the menstrual cycle is irregular.