The Dynamics of Conception and Fertility:
What Happens During Ovulation?

> Reproductive Hormones and Ovulation
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> The Luteal Phase
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> Stages and Processes of Ovulation

Predicting your most Fertile Periods
Understanding how the menstrual cycle functions - and what happens during ovulation - is key to the successful prediction of ovulation. But what happens exactly? Let's look at the dynamics of fertility and conception.

During your menstrual cycle, there are far more infertile days than fertile days. The fertile days are those when there is a possibility of conceiving a baby. However, within your fertile period - the window of opportunity for conception - there are also days of "peak fertility". Identifying these peak times, and planning accordingly, can help maximize your chances of becoming pregnant.

The Dynamics of Fertility
A woman's fertile period during her menstrual cycle, on average, lasts about 7 days. However, the most fertile period consists of the few days before ovulation. There are a number of reasons why this is the most fertile time. First of all, the amount of cervical fluid increases - and the consistency of the mucus changes substantially (from being sticky and cloudy to becoming transparent, white, and slippery). The purpose of this change is to create a healthy medium for the sperm to survive and travel in. Given a fertile environment, sperm can live several days. The egg, on the other hand, can live only 24 hours - so timing is important. At the moment of ovulation, the body temperature begins to rise to create a warmer, more hospitable environment for a fertilized egg. Also, the cervix will start to rise, soften, and begin to open up.

Hormones and Ovulation: The Release of the Egg
During ovulation, a number of different hormonal changes take place. Early in the menstrual cycle, a hormone called Follicle Stimulating Hormone - or FSH - enables your ovaries to nurture eggs. Within the ovaries, follicles house each individual developing egg. The follicles that hold the eggs will secrete estrogen. As the menstrual cycle progresses, the follicle containing the developing egg moves toward the surface of the ovary. Immediately before ovulation, the follicle begins secreting estrogen and progesterone. Estrogen helps the uterine lining thicken and expand, and increases blood flow to the uterus. Progesterone causes the glands of the uterine lining to form secretions that help nourish a fertilized egg once it implants in the womb.

Image of reproductive organs and follicle at the moment of ovulation.

By definition, ovulation is the process of an ovary releasing an egg from the follicle - permitting the egg to float down the fallopian tubes. On average, the first phase of the menstrual cycle last two weeks.

Directly prior to ovulation, another hormonal change takes place - the LH Surge. LH (or Luteinizing Hormone) is the hormone that actually facilitates ovulation: it causes the egg to separate from the ovarian surface. Ovulation predictor tests function by detecting this LH Surge, thus alerting the woman that ovulation is about to take place.

Click the link to read more about Hormones and Ovulation - and what the various representative lines in the graph above mean.

Once released from the ovaries (post-ovulation), the egg can survive for about 24 hours. This means that sperm (which can live several days, under ideal conditions) must be present to fertilize the egg. Following ovulation, the egg enters the fallopian tube and continues toward the womb. Typically, conception - the uniting of the egg and the sperm - will take place in the fallopian tube, and then the fertilized egg will continue its passage to the uterus and implant in the uterine wall. For pregnancy to take place, fertilization of the egg must be followed by a successful implantation.

Following ovulation, the luteal phase begins, marked by an increase of the hormone progesterone, which strengthens the uterine lining (endometrium), causes the body temperature to increase, facilitates changes in the cervical fluid, and alters the position of the cervix.

Within 24 hours, if the egg has not been fertilized, it will simply disintegrate after reaching the uterus. Without fertilization - and implantation - the levels of others hormones will ultimately drop during the luteal phase, causing the lining of the uterus to break down and shed - referred to as menstruation, or a woman's "period".

Implantation and Pregnancy
Fertilization occurs when a sperm penetrates the egg - and this typically takes place in one of the fallopian tubes. The fertilized egg then travels to uterus and implants in the uterine lining. At this point, the egg - and developing placenta - begin to release hCG (Human Chorionic Gonadotropin). The presence of hCG will help facilitate the continued production of progesterone - essential for a fertile, hospitable environment for the implanted egg. The hormone hCG will increase - and show up in a woman's blood and urine - making hCG a prime marker for pregnancy detection. Home pregnancy tests function by detecting hCG in a woman's urine.

Return to: Understanding Your Menstrual Cycle

Read More About > The Luteal Phase
Related Topics > Ovulation FAQ
- J. Pepperin, 2000-2007