A luteal phase calculator is a simple computer program that estimates the length of a woman's luteal phase, which is the number of days between ovulation and the onset of the next menstrual cycle. It is different than an ovulation calculator, but they are often used together as an accurate ovulation date is necessary to calculate your luteal phase. The length of the luteal phase is important if you are trying to conceive, since this is the phase when a fertilized egg implants itself onto the uterine wall, and your body begins to prepare for a viable pregnancy. Luteal phase calculators are generally free and widely available online from various fertility websites; a simple search will turn up several different calculators for you to try.
The luteal phase is named for the corpus luteum, which is yellowish glandular tissue that forms after an egg has been released. This tissue is important because it stimulates the production of progesterone, an important hormone for the successful implantation of a pregnancy. Progesterone warms the body and causes the lining of the uterus to thicken, preparing to nurture the pregnancy. The average luteal phase lasts 14 days, but variations between 10 and 16 days are considered normal. A luteal phase of less than 10 days may prevent the pregnancy from implanting properly.
In order to determine your luteal phase using a luteal phase calculator, you must have two key pieces of information: the date of ovulation, and the date that menstruation began after ovulation. The most accurate way to determine the date of ovulation is to use an over-the-counter ovulation predictor kit, which measures luteinizing hormone, or LH levels. During ovulation and immediately before, this hormone surges and can be detected with a simple urine test. Ovulation can also be predicted by using the basal temperature method, although this is less accurate than an ovulation predictor.
The period around ovulation is the most fertile time in your cycle, which means this is the optimal time for sexual intercourse if you are trying to conceive. However, ovulation can occur at different times in the cycle from month to month, so the test you took last month may not be accurate in telling you when your most fertile time frame will be next month. The luteal phase, on the other hand, is remarkably consistent from month to month in most women. Using the luteal phase calculator can tell you when you are most likely to conceive, even if your menstrual cycles are irregular.
If the luteal phase is too short, generally less than 10 days, there is not enough time for implantation of the egg cell to take place. Using a luteal phase calculator can alert you to problems with the length of your luteal phase which may be keeping you from conceiving. A luteal phase defect, or LFD, is associated with a shortened luteal phase and sometimes inadequate progesterone production. LFD can be treated with progesterone therapy, and some herbal medications are also thought to support the production of progesterone. Talk to your gynecologist or naturopath if you suspect you may have LFD and discuss what treatment options are available.