The luteal phase is the second phase of the menstrual cycle, after ovulation. The luteal phase lasts from the day of ovulation to the day before a woman's next period. It averages 14 days, although the length of time can vary from woman to woman. The phase ends either in pregnancy or the start of menstruation and the beginning of the next menstrual cycle.
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Luteal Phase Description
The luteal phase begins with a surge of luteinizing hormone, which causes a mature egg to burst through the ovary wall. The egg begins a journey along the Fallopian tube toward the uterus. The follicle from which the egg is released (known as the corpus luteum) produces progesterone that thickens the lining of the uterine wall in preparation for potential implantation. Progesterone is produced for 12 to 16 days by the corpus luteum. If the egg is fertilised, the corpus luteum continues to produce progesterone to support the embryo until the placenta develops. An egg remains viable up to 24 hours. If fertilisation does not occur, the egg disintegrates, hormone levels decrease and the lining of the uterus sheds.
A woman can track the start of her luteal phase by tracking the end of her ovulation phase, noting the colour and consistency of her cervical fluid and monitoring her body temperature. Just before and during ovulation, cervical discharge becomes wet, slippery and resembles the texture of egg whites. A slight rise in temperature is the best indication of ovulation. Fertility monitors and ovulation kits are available to identify ovulation, too. The luteal phase begins just after ovulation.
Changes in the luteal phase take place during perimenopause, the transition from regular cycles of ovulation to infertility, or menopause. This usually occurs in women between ages 45 and 55 years, although timing and symptoms vary among women. During this transition, the luteal phase gradually ceases, along with the menstrual cycle itself. Levels of oestrogen diminish, the ovaries shrink, ovulation and menstruation become irregular and increasingly infrequent. Eventually, the luteal phase ends completely. A woman enters menopause when she has not menstruated for more than one year.
Luteal Phase Defect
In pre-menopausal women, short or irregular luteal phases may affect fertility. The disruption of a normal menstrual cycle is known as a "luteal phase defect" or an "inadequate luteal phase." This occurs when a woman does not produce enough progesterone to thicken the uterus lining and support the development of an embryo. Injections of progesterone or follicle stimulating hormone (FSH) can be administered if it is suspected that a woman has luteal phase defect. The concept luteal phase defect is controversial, however, and the role it plays in infertility is uncertain.
Other disorders also affect the luteal phase of a woman's menstrual cycle. The abnormal secretion of FSH and luteinizing hormone due to factors such as stress, extreme physical exercise or rapid weight loss or gain can disrupt the luteal phase, causing irregular or absent periods.
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- American Pregnancy Association: Understanding Ovulation; August 2006
- American Pregnancy Association: Ovulation Kits and Fertility Monitors; March 2005
- The American Congress of Obstetricians and Gynecologists: Midlife Transitions: Perimenopause to Menopause; December 2010
- Mayo Clinic: Perimenopause -- Definition; September 2010
- "The New York Times;" Health Guide -- Luteal Phase Defect
- Mayo Clinic: Female Infertility -- Causes; January 2010