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Menstrual Cycle I
To better understand the complicated processes required to cause implantation in the endometrium (uterine lining), we’re going to give you a short overview here of the natural process that occurs during the menstrual cycle:
A woman’s menstrual cycle usually lasts approximately 28 days. It begins with the first day of menstruation and ends with the day before the next menstruation. During menstruation, which can last around 3 to 7 days, a dominant follicle begins to grow in one of the two ovaries.
A precisely aligned interaction between ovary and pituitary gland (hypophysis) controls the growth of the follicle.
Follicles generally contain one egg cell (ovum).
This one follicle then bursts at the right point in time (ovulation) to release its contents, which include follicular fluid and an egg (oocyte).
Menstrual Cycle II
Ovulation may not occur if the follicle has not grown large enough. This is often the case with older women.
After ovulation, the follicle develops into the corpus luteum.
The function of the corpus luteum is to influence the conditions for implantation in the uterus (womb) so that an embryo can implant.
In a healthy woman, the life span and function of the corpus luteum is geared towards supporting the development of pregnancy during the first twelve days.
If pathological circumstances intervene to shorten the life span of the corpus luteum (less than 10 days) or restrict the function of the corpus luteum in such a way that the endometrium (uterine lining) cannot be appropriately prepared for the possible implantation of an embryo, this is called luteal phase deficiency (or luteal phase defect).