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Interactive Tool: When Are You Most Fertile?

What does this tool help you learn?

This interactive tool estimates your peak fertility period, also known as your "fertile window." This is when you are most likely to get pregnant. Do not use this tool to prevent pregnancy.

In the tool, you will enter the typical length of your menstrual cycle, and you will click on the first day of your last menstrual period.

  • To know how long your cycles are, track the number of days on a calendar for 2 or 3 months or cycles. Your menstrual cycle begins with the day your period starts and ends the day before your next period starts.
  • If you do not know the number of days in your menstrual cycle, you can use 28 days. This is the average length of a menstrual cycle. But if your cycle is longer or shorter than that, or if it is not always the same length, this tool will not predict your fertile window very well.

Fritz MA, Speroff L (2011). Clinical Gynecologic Endocrinology and Infertility, 8th ed., Philadelphia: Lippincott Williams and Wilkins.

What do the results tell you?

Your "fertile window" is up to 6 days long, once a month. It includes:

  • The day you ovulate. This is when you have the best chance of becoming pregnant. (A human egg usually lives for only 12 to 24 hours after ovulation. This is why you are not likely to get pregnant by having sex a day after you ovulate.)
  • The 5 days before ovulation. This is because sperm can live in a woman's body for 3 to 5 days after sex. When an egg is released, one of these sperm is ready to fertilize it.

If you want to become pregnant, try to have sex every day or every other day from your first fertile day to your last fertile day.

What's next?

If your periods are irregular, this calculator is not a good way to predict your ovulation dates. Do not use this tool to prevent pregnancy.

For more information, see the topics Fertility Awareness, Pregnancy, and Fertility Problems. If you are looking for information on birth control, see the topic Birth Control.

References

Other Works Consulted

  • Fritz MA, Speroff L (2011). Clinical Gynecologic Endocrinology and Infertility, 8th ed., Philadelphia: Lippincott Williams and Wilkins.

Credits

Current as of: February 11, 2020

Author: Healthwise Staff
Medical Review: Adam Husney, MD - Family Medicine
Kathleen Romito, MD - Family Medicine
Kirtly Jones, MD - Obstetrics and Gynecology, Reproductive Endocrinology

COVID-19 Updates

Do you ever feel at times due to life being so busy you put your health on hold? Now is the time to take care of you! For many of our patients we have postponed your annual exam by moving it out a few months in response to COVID-19, but we still want to make sure we have the opportunity to take care of you from afar. If you are our patient and have not had the opportunity for us to review your cancer family history with you, or maybe you have just put this on hold, here is the opportunity for you to fill out your information in a few quick steps online to see if testing is right for you! This questionnaire on your medical history will be posted to our website as well to access and to complete. So take control of your health today! We will be happy to direct you to right resources and follow up with you for any questions you may have.

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