The corpus luteum is a temporary structure that forms in the ovary after an ovarian follicle has released an egg during ovulation. It is an essential structure for reproduction. This produces hormones that have an essential role in preparing the uterus for pregnancy and maintain it during the first weeks of gestation.
How is it formed?
The corpus luteum is formed from the cells of the ovarian follicle after ovulation and develops into a hormone-secreting glandular structure. This structure is composed mainly of lutein cells, that is, those that produce the hormone progesterone. It should be remembered that progesterone is essential for the maintenance of the endometrium, since it will be this inner layer of the uterus that thickens, in preparation for the implantation of the embryo.
What are its phases?
- Formation phase: After ovulation, the mature ovarian follicle transforms into luteal cells and begins to produce the hormone progesterone. These luteal cells group together to form the corpus luteum.
- Growth phase: During the first few days after formation, it increases in size and continues to produce progesterone.
- Maturation phase: As it matures, its production of progesterone increases and it begins to produce small amounts of estrogen.
- Degeneration phase: If the egg is not fertilized, the corpus luteum begins to degenerate and hormone production decreases. This causes menstruation and the start of a new menstrual cycle.
- Maintenance phase: If the ovum is fertilized and implants in the endometrium of the uterus, the corpus luteum persists and continues to produce hormones, mainly progesterone, which are essential to maintain the pregnancy.
- regression phase: As the pregnancy progresses, its function gradually decreases. Finally it degenerates completely, since the placenta takes over the production of the hormones necessary to maintain the pregnancy.
It is important to note that the duration and intensity of each phase of the cycle can vary according to each individual and each menstrual cycle.
Relationship between the corpus luteum and pregnancy
If the ovum is fertilized, the corpus luteum persists and continues to produce progesterone until the placenta forms and takes over production of this hormone. The progesterone produced helps to thicken the endometrium of the uterus, preparing it for embryo implantation and providing a suitable environment for the development of the fetus in the early stages of pregnancy. Additionally, progesterone also helps relax the muscles of the uterus and prevent early contractions, which could lead to a miscarriage.
If the egg is not fertilized, the corpus luteum degenerates and progesterone production decreases, which causes menstruation and a new menstrual cycle begins.
When does the corpus luteum appear?
The corpus luteum appears after ovulation, when a mature ovarian follicle releases an egg into the fallopian tube. Ovulation normally occurs on day 14 of the menstrual cycle, although this can vary based on cycle length and other individual factors.
After ovulation, the cells of the ovarian follicle that surround the released ovum become luteal cells and begin to produce the hormone progesterone. These luteal cells group together to form the corpus luteum.
And when does it disappear?
As the pregnancy progresses, the function of the corpus luteum gradually declines. Finally, it degenerates completely, since the placenta takes over the production of the hormones necessary to maintain the pregnancy. This usually occurs around the 10 to 12 week of pregnancy, by which time the corpus luteum is no longer needed and disappears naturally.
Can there be a corpus luteum without pregnancy?
Yes, it is possible to exist without pregnancy. As we have mentioned, this is formed after ovulation, but before the possible fertilization of the egg occurs. When the egg is not fertilized, the corpus luteum persists for about 12 to 14 days, producing the hormone progesterone to prepare the uterus for possible implantation of an embryo.
In addition, in some cases, it may occur without ovulation, which is known as a non-ovulatory corpus luteum. This can occur when the ovarian follicle matures, but does not release the egg, which can cause a corpus luteum to form without actual ovulation. This can cause symptoms such as abdominal pain, bloating, and menstrual changes. In general, if there is any question about the presence or absence of the corpus luteum, it is important to have a medical evaluation to determine the proper diagnosis and treatment.
At IVI we can help you
If after a year of seeking pregnancy it is not achieved, the time has come to consult with a specialist in reproductive medicine. You can contact us by calling 900847300 or through the form to request an appointment at IVI. We have more than 30 years of experience leading the field of reproductive medicine and we have more than 30 clinics in Spain.
