The luteal phase often gets a lot of attention relative to the follicular phase because of its relationship with pregnancy, either in preventing one or becoming pregnant.
It is also essential for the initial maintenance of the early pregnancy.
An understanding of this phase of the cycle is therefore necessary for every woman.
This article presents the necessary basic medical information, simply presented for every woman to understand including its importance, associated uterine and ovarian changes, luteal phase length and common abnormalities seen in some women.
It is the last phase of the ovulation cycle. It is the period that follows the release of the egg (ovulation) to the day before menstrual flow. Because this phase includes the days that follow ovulation, it is commonly referred to as "Days Post Ovulation(DPO)".
The major contribution of this phase is pregnancy related. It is geared towards making "all ready" to properly establish an early pregnancy. Any abnormality in it thus makes it difficult to retain an early pregnancy.
It is associated with changes in hormonal levels, ovarian follicles and uterine endometrium.
At ovulation, the mature follicle ruptures and releases the egg. The remnants of this follicle transforms into another structure called the corpus luteum(yellow body, literally). The cells called granulosa cells which surround the ovum as it matures during the follicular phase become filled with secretions and fat after ovulation, and are called lutein cells or yellow cells.
The main particularity of the lutein cells is that they are capable of secreting the hormone called progesterone and also some estrogen.
The outcome of the corpus luteum depends on the outcome of the egg-whether it is fertilized to produce a pregnancy or not.
As with the rest of the ovulation cycle, the observed changes are always due to hormonal changes. The main hormone that controls the activities of the luteal phase is progesterone.
The main effects of progesterone during this phase are
These hormonal changes are also responsible for the sore breasts after ovulation that occur during this phase.
The lifespan of the egg after its release is 24 hours or less.
If fertilized, usually in the fallopian tube, it moves through the tubes into the uterus. Within the uterine cavity, the blastocyst digs into the endometrium and becomes embedded within it. This is called implantation.
It usually takes about 5 to 6 days following ovulation for the fertilized egg to arrive the uterine cavity.
Within the endometrium, the blastocyst requires the support of the endometrium to stay alive. The endometrium itself requires progesterone from the corpus luteum to maintain the conducive environment. If the corpus luteum does not stay until the blastocyst is fully implanted and starts producing hCG to support it, the pregnancy will not be supported. This is the central abnormality of the disease called luteal phase defect.
Why is this phase apparently so important for most women? First, I have realized that the majority of women who have asked for more information on this phase are those who are seeking to achieve a pregnancy.
The medical importance and reason for the popularity of this phase amongst women are due to the factors below.
The length of this phase is critical for the survival of an early pregnancy. It is the number of days from the moment after ovulation to the day before menses, normally ranging from 12 to 16 days. A shorter length than 12 days is called Luteal Phase Defect(LPD) and is often associated with miscarriages or infertility. It can usually be measured by using ovulation signs or hormonal kits.
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