A luteal phase is one of the three phases of the menstrual cycle that is necessary for reproduction. This is the phase that occurs after ovulation and continues until the day before a woman’s next period. This phase ordinarily lasts about two weeks (14 days) and is often used with an Ovulation Calendar to calculate the time of ovulation. The luteal phase may vary among women, but the length is usually relatively the same for the same woman.
The purpose of the luteal phase is to produce progesterone that prepares a woman’s body for pregnancy. The length of this phase is usually constant and can be used to establish the time of ovulation with the woman’s menstrual cycle. This is important in planning or avoiding pregnancy. An Ovulation Calendar such as the “My Calendar” used by some women can use the length of the luteal phase and the number of days in the menstrual cycle to determine when ovulation will occur. A simple example is seen with a 28-day cycle and a luteal phase that is twelve days long. According to this information, ovulation should take place on day sixteen of the cycle. The calculation used to determine this date is the days of the luteal phase (12) subtracted from the days of the cycle (28).
The average length of the luteal phase for most women is fourteen days. Another way to find the length of a luteal phase can be determined by charting the Basal Body Temperature (BBT), which is known as the waking body temperature. The BBT rises after ovulation. Count the number of days from the rise in the BBT until the menstrual period, will provide the length of a specific woman’s luteal phase. Using the steps below, BBT can be charted to determine a woman’s personal luteal phase:
The length of the luteal phase is the period of time that begins on the day ovulation occurs, and ends on the day before the menstrual period begins. As previously noted, this tends to be about fourteen days.
Any luteal phase can be determined by charting the waking temperature every day for a month, as spelled out above. However, if a woman just needs an estimate, she can use the average of fourteen days, which is the length of the luteal phase for most women. Using the acceptable average will give a good approximation on an Ovulation Calendar for the time a woman will be generally the most fertile.