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Emergency Dept: 314-205-6990 Patient Billing: 888-924-9200
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Pregnancy Health Center

Ovulation Calculator

Some women have no idea when they've ovulated, while others can tell the exact moment it happened. In a typical menstrual cycle, an egg grows within a follicle in the ovary for two weeks, starting on the first day of your menses. Then, a hormone called lutenizing hormone (LH) rises dramatically and triggers the egg to be released from the ovary. The release of the egg is called ovulation.

When you ovulate, one of your eggs is carried into the fallopian tube. If a man's sperm makes its way to the same spot within the next 6 to 12 hours, it may fertilize that egg. You're not actually pregnant until the fertilized egg, called a zygote, travels the rest of the way down the fallopian tube and attaches itself to the wall of your uterus or, in unfortunate cases, attaches elsewhere and causes an ectopic pregnancy.

The catch: The average egg lives for fewer than 24 hours, and the average sperm lives for less than 72 hours, so they have to get acquainted during the first few hours after sex if you're going to conceive. The moral of the story: If your goal is to get pregnant, you should aim to make love at least every other day during the middle of your cycle. Studies have shown that sex must occur before ovulation in order to become pregnant. Kits that detect LH and measure your basal body temperature can help predict the exact time that you will be ovulating. Ideally, you should have intercourse on the day before, of, and after the LH kit turns positive.

Use the following tool as a quick way to get an idea of when you ovulate. Please note that ovulation is tricky to pinpoint; see our timing and fertility article for more information.

Number of Days in CycleOvulation Day
(Counting from First Day of Cycle)

NOTE: Many factors can affect the accuracy of this tool, including irregular menstrual cycles. This calculator should not be used as a method of preventing pregnancy.

Review Date: 12/9/2012
Reviewed By: Irina Burd, MD, PhD, Maternal Fetal Medicine, Johns Hopkins University, Baltimore, MD. Review provided by VeriMed Healthcare Network.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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St. Luke's Hospital - 232 South Woods Mill Road - Chesterfield, MO 63017 Main Number: 314-434-1500 Emergency Dept: 314-205-6990 Patient Billing: 888-924-9200
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