Women’s Fertility Cycle

Women often ask, “What exactly is occurring inside my body during my monthly fertility cycle?”.

woman’s ovaries contain her eggs, the special cells of human reproduction. Hormones regulate a woman’s fertility cycle, which usually spans a 28 to 30 day period.

A woman’s fertility cycle begins on the first day of the menstrual period.

Earlier in the cycle, a single egg begins the process of maturing. That egg develops inside of a fluid-filled sac called the follicle. The follicle increases in size during the first half of the menstrual cycle. Halfway through the cycle, the follicle pops or ruptures, releasing the egg, which then passes into the Fallopian tube. This is called ovulation.

If a healthy sperm is present in the Fallopian tube, the egg will be fertilized, leading to conception. As the follicle grows, it produces an essential hormone called estrogen. After the egg is released, that follicle shrivels up and becomes something called the corpeus luteum and begins making another important hormone called progesterone.

Here is a diagrammatic representation of the hormonal changes that occur during the menstrual cycle. As you can see, estrogen rises to a peak just before ovulation and then falls dramatically. After ovulation, estrogen is still being made, but now progesterone becomes the dominant hormone. These hormones changes are critically significant for normal fertility.

Estrogen goes right back to the follicle, causing it to mature completely. Estrogen stimulates the lining of the womb to build it back up after it was shed during the menstrual period in preparation for the baby to implant. And estrogen travels through the bloodstream to the bottom part of the womb, which is called the cervix and causes a clear, slippery fluid to be produced.

This special fluid, in and of itself, plays an important role in a couple’s ability to conceive. First, when that fluid is not present in the vagina, sperm die within hours. The egg only lives for 12-15 hours, which would make the fertile window very short. When the fluid is present, and it is usually produced by a woman’s body about 4-5 days before ovulation. It protects the sperm from the acidity of the vagina and allows the sperm to live for up to 5 days, lengthening the fertile window.

At the molecular level, the cervical fluid is also critical because it creates swimming channels for the sperm, which allow the sperm to reach the egg.

Learn more about female fertility on americanpregnancy.org.