Of the four phases of a woman’s monthly cycle, ovulation is the shortest, yet it is the most important one for a woman trying to get pregnant. Occurring on the fourteenth day of a regular 28-day cycle, ovulation generally lasts from 24 to 72 hours. Knowing when ovulation occurs in your cycle can help you pinpoint the time when you are fertile. Ovulation kits are available for those who need help tracking their cycles, but many women chart their fertility and ovulation cycles without help. This section will teach you about the importance of hormones to ovulation—how they control a woman’s sexual desires and menstrual cycles, and especially how they affect your body before and after ovulation.

What Is Ovulation?

Ovulation is an essential part of the menstrual cycle. During this phase, a mature egg (also known as an ovum) is released from an ovarian follicle. The egg then travels down the fallopian tube, where it may meet a sperm cell and become fertilized. The ovulation process is controlled by the hypothalamus, a gland in the brain that signals your body to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH causes one or more of the eggs in the ovary to activate. The layer of cells surrounding the egg increases and becomes a welcoming environment for a sperm cell. LH triggers the follicle to release the egg. Meanwhile, the lining of the uterus thickens to prepare for a fertilized egg. If the egg passes through the fallopian tube unfertilized, then it exits the body along with the uterine lining that sheds as a part of menstruation.

Your Fertile Window

During each monthly cycle, you have a small window of opportunity to conceive. This is when the egg is viable, or ready to be fertilized. This “fertile window” typically starts a few days before ovulation and ends after ovulation. If you are trying to conceive, it is best to have sex during this time. Because sperm can live in a woman’s body for three to six days, you can have sex almost a full week before ovulation and still become pregnant, but having sex on the day you ovulate increases your chances of conceiving.

How Can You Tell When You Ovulate?

Here are a few ways you can determine when you are ovulating. For most women, using more than one method is best. This is particularly important if your periods are irregular.

Count the days in your cycle. If your menstrual cycle is normal and lasts about 28 days, then you can count 14 days from the first day of your period to find out when ovulation is likely. Ovulation usually occurs halfway through your menstrual cycle. However, because the length of normal menstrual cycles can be longer or shorter than 28 days and vary from month to month, simply counting the days of your cycle will not always work. To get an idea of what is normal for you, keep track of your menstrual cycle for a few months.

Take your basal body temperature. This is done with a basal body thermometer (available at your local pharmacy). Your basal body temperature tends to decrease before ovulation; at ovulation, it is at its lowest, and right after ovulation occurs, it spikes. You must take your basal body temperature in the morning before you get out of bed or sit up. This must be done every morning for a few months, or a few cycles, in order to determine a pattern that shows a decrease in your temperature and a noticeable spike. A woman trying to get pregnant should try to have sex during the time her temperature is at its lowest.

Monitor your cervical mucus. During your menstrual cycle, the amount of cervical mucus your body generates changes. This generally coincides with a rise in the levels of hormones that prepare the egg to be released from the ovary. Some women may see evidence of increased cervical mucus on their underwear on the days leading up to ovulation. This discharge is white or cloudy and typically has a stretchy consistency. As ovulation approaches, the mucus increases and turns thin and clear. This increase in mucus/discharge can occur after ovulation has occurred, so it is not always the best predictor of ovulation. However, in combination with counting your days and taking your basal body temperature, it can help you determine when ovulation is likely.

Use an ovulation kit. Ovulation kits can alert you to ovulation up to 24 hours in advance. These kits are available at pharmacies, and they are easy to use. Like home pregnancy tests, they require you to urinate on a stick and wait for the indicator to tell you whether you’re about to ovulate. Ovulation kits cannot tell you whether the follicles on your ovaries contain a mature egg or whether the egg is of good quality. These kits are generally not cheap.

Pay attention to any abdominal cramping. A small percentage of women have mild pain or cramping in their lower abdominal area during ovulation. This is known as mittelschmerz (German for “middle pain”). It is thought to signal the maturation or release of an egg from an ovary. The pain often occurs on one side, indicating which ovary the mature egg is being released from.

Ovulation Complications

In some women, ovulation may occur infrequently or not at all. This condition is called anovulation. These women usually have infrequent periods (oligomenorrhea), which can decrease the chances of conception and make it difficult to detect fertile times. Ovulation disorders can occur for many reasons, but fortunately, many of them can be treated.

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