Female Hormones & The Menstrual Cycle

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Women’s Reproductive Hormones

Throughout this process, the hormones within the womb are changing the nature and the architecture of the womb lining. Under the influence of oestrogen and progesterone. The nutritional and receptivity status of the womb lining changes as it prepares for the blastocyst to implant. The rising levels of oestrogen cause the womb lining to thicken and following ovulation, progesterone levels begin to rise. It’s this rise in progesterone following ovulation that causes the womb lining to mature and develop in preparation for the embryo. At this point, around six days after ovulation has taken place, the blastocyst will start to implant into the womb lining. If successful, around eight to nine months later, the baby will be born.

The Menstrual Cycle

 It’s important to understand the fine balance of hormones that control the menstrual cycle. when looking at natural conception. The menstrual cycle is essential to follicular development, ovulation and successful implantation of an embryo in the uterus. On average, the menstrual cycle lasts for around 28 days, though it can vary in length considerably from around 21 days, right up to as much as 35 days. Under the influence of the menstrual hormones, the womb lining or the endometrium is prepared each month for an embryo to implant. Under the influence of oestrogen the lining thickens, but if fertilization of an egg fails to take place, or perhaps the use of contraception prevents normal fertilization, then the lining sheds and a period happens.

There are several phases that we recognize during the menstrual cycle. The start of the menstrual cycle is designated by a period. Following this over the first 14 days of the cycle or the follicular phase, the dominant follicle is recruited. After an egg is released during ovulation, the luteal phase occurs, and it’s during this point that an embryo has the opportunity to implant.

The Follicular Phase

The start of the follicular phase is determined by a period starting as the endometrium is shed. It’s during this phase that a new wave of follicles that exist in the ovaries begin to mature and develop under the influence of follicle stimulating hormone or FSH. Usually during this time, FSH levels rise in the blood and the ovaries contain thousands of follicles with immature eggs in them.

And under the influence of FSH a dominant follicle will gradually grow and prevail, all of the other follicles that month, wither away. The dominant follicle under the influence of FSH enlarges and during this follicular phase reaches maturity and it’s at this point ovulation takes place. During this phase, as the follicles grow, oestrogen is produced, the oestrogen levels rise in the blood, which causes the wound to thicken.

Egg Maturation & Ovulation

 In the lead up to ovulation follicles will develop under the influence of the hormones in the ovary. This involves a dominant follicle enlarging, and eventually following a surge in luteinizing hormone, around the middle of the cycle, the follicle will mature and rupture to release the egg. The final process of maturation of the egg occurs in the dominant follicle as the follicles enlarge and approach release of the egg. This involves the egg shedding half of its chromosomal footprint as it gets ready for fertilization by a sperm. As the egg is released, the fimbria or finger-like projections of the fallopian tubes sweep across the surface of the ovary collecting the egg and gathering it into the tube, and at the distal end of the tube, it then begins its journey to meet the sperm.