Crash Course in Human Reproduction

Here's a quick refresher course in human reproduction to help you plan for pregnancy. It helps to know how your reproductive cycle works, and when the timing is right to try to become pregnant. Each month, a woman's body goes through hormonal and physical changes called the menstrual cycle. This cycle averages about 28 days long, with the start of menstrual bleeding as day one. When menstrual bleeding stops, hormones stimulate the uterus (or womb) to begin to build a soft, thickened lining. This is in preparation for pregnancy. About a week later, near day 14, ovulation occurs as an egg cell (called an ovum) is released from one of the ovaries (two female reproductive organs located in the pelvis) and is drawn into the nearby fallopian tube. When male sperm cells enter the woman's vagina during intercourse, they travel up into the uterus and out through the fallopian tubes. Pregnancy results when the egg is fertilized by a single sperm cell as it travels down the fallopian tube.

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Ovulation Explained

Although most women ovulate around day 14, others may ovulate a few days earlier or later, depending on the length of their menstrual cycles. You may not notice any signs of ovulation, but some women may have some minor discomfort in their lower abdomen. Others may have spotting or bleeding. Many women also notice an increase in clear mucus from their vagina a few days before ovulation. Because the sperm tend to move slowly through the woman's uterus and tubes and can live for several days, the timing doesn't have to be perfect. A woman is generally most fertile (able to become pregnant) a few days before, during, and after ovulation.

After the egg is fertilized, it moves down the fallopian tube and into the uterus to implant into the soft lining. The lining continues to thicken and grow to provide a nourishing environment for the early pregnancy. If the egg is not fertilized, the body signals the hormones to change. The thickened lining is shed with menstruation and the cycle begins again.

Most women are able to get pregnant within about 12 months of actively trying to conceive. If you want to know more about timing, or have concerns about your menstrual cycles, talk with your physician.