Female factors that influence fertility are directly related to the menstrual cycle. The menstrual cycle is how the female reproductive system prepares for pregnancy. If there is any deviation from the normal process of the cycle or its phases, fertility problems appear. Reproductive theory says the menstrual cycle lasts approximately 28 days and that ovulation takes place around day 14. However, only 15% of women have cycles of 28 days, and cycles between 21 and 35 days are considered normal. In this article, we look at how the menstrual cycle affects fertility in more detail, including when to try for a baby.
The Two Processes of your Menstrual CycleThe menstrual cycle is a hormonally-controlled process that consists of two simultaneous cycles: The ovarian cycle and the endometrial cycle.
The Ovarian CycleThe ovarian cycle aims at the maturation of the oocytes and hormone production so that if fertilization occurs, the embryo can be implanted. Therefore, the ovulation cycle is important if you’re considering when to try for a baby. The ovarian cycle consists of 2 phases:
- Follicular phase. This is responsible for the maturation of follicles. Only one follicle will ultimately mature and become a Graafian follicle; the rest will be transformed into fibrous bodies. The main hormone that acts in this phase is FSH (Follicle Stimulating Hormone).
- Luteal phase. LH produces transformations in the follicle and turns it into a corpus luteum. The corpus luteum is able to secrete estrogen, progesterone, and produce changes in a woman’s body.
The endometrial cycleThe endometrial cycle’s function is to prepare the endometrium (the mucous layer of the uterus) so that it can nourish the fertilized egg in case of implantation. It is divided into 3 phases:
- Menstruation. This is the shedding of the endometrium along with the inactivation of the corpus luteum. It lasts between 2 and 7 days, depending on the woman. It is the first phase of the cycle and begins the count at day one, marking the beginning of the current cycle and the end of the previous.
- Proliferative phase. The endometrium has been shed during menstruation, has a thickness of 1 or 2 mm, and will begin to thicken again. Estrogen acts by converting the endometrial glands: Before they were straight, narrow and short; now they become long and twisted.
- Secretory phase. Progesterone further increases the thickness, the number, and the size of the blood vessels that nourish it. The endometrial glands gain the ability to accumulate glycogen, a carbohydrate energy reserve that can be transformed into glucose when the body requires it.