The luteal phase is the second half of a normal menstrual cycle, beginning the day after ovulation and continuing until menstruation begins. Unlike the pre-ovulatory phase, which can vary in length from month to month, a woman typically will have a very set luteal pattern. Most women experience a luteal phase between 10-16 days, with 14 days being very common. A long luteal phase is when the body continues to produce increased levels of progesterone for more than 16 days after ovulation. Long luteal phases are very rare, but can affect fertility and conception planning.
Just before ovulation, the female system experiences a surge in the hormones that promote implantation of a fertilized egg. This spike typically presents as an slight increase in temperature and results in the release of progesterone to aid possibly fertile eggs in their next stage of development. This increased level of progesterone combined with ovulation is what indicates that a woman has entered the luteal phase of menstruation.
Typically, the increased flow of progesterone decreases if no fertilization has occurred, allowing menstruation to begin. For most women, doctors recommend assuming that the luteal phase will last about 14 days. If a long luteal phase is suspected, determining the date of ovulation is vital to understanding when the luteal phase actually began. Keeping a daily record of body temperature can also give a more clear picture of when the temperature spike associated with the phase began and ended. Certain hormone-based blood tests can also help determine if a woman has a long luteal phase.
It is possible to mistake other conditions for a long luteal phase. The pre-ovulatory phase is typically between 12-14 days, but can vary based on lifestyle factors. Increased stress, a change in diet, or increasing or decreasing physical exercise can delay or speed ovulation from month to month. If ovulation is delayed from day 14 to day 17 by lifestyle changes, it is easy to think a longer luteal phase has occurred. Most women with a long luteal phase have it consistently, so a rare delayed period is more likely a result of late ovulation.
For women trying to get pregnant, a long luteal phase can cause frustration and concern if misunderstood. Many women may realize that their cycle has gone on for more than 28 days and think this indicates pregnancy, when in fact the long luteal phase has simply not allowed for menstruation to begin. Additionally, high progesterone and extended increased temperature can indicate pregnancy, so even women monitoring their temperature daily may be confused by this condition.
Although a long luteal phase can be inconvenient, once discovered it is typically easy to work around. Since the phase is typically fixed, women can simply alter their calendars to fit the likely day of menstruation based on the longer length of their individual phase. There is little information that suggests that a long luteal phase can result in infertility or miscarriage, although studies on this subject are not readily available. If a long luteal phase is suspected, speaking to a gynecologist may be useful in obtaining more information and possibly undergoing necessary tests to determine if the condition exists.