Fertile Window

Definition - What does Fertile Window mean?

The fertile window is the time in a woman's cycle when she is most likely to get pregnant. It consists of the few days prior to ovulation, and the day of ovulation itself.

FertilitySmarts explains Fertile Window

Sperm can live in the female reproductive tract for several days. However, eggs typically live only one day after ovulation if not fertilized. As such, the highest chance of conception occurs when sperm is introduced in the days preceding ovulation, or on the day of ovulation itself.

The fertile window for an individual woman can be identified by tracking changes to her body that occur as ovulation approaches. Changes to basal body temperature, cervical mucus, and cervical position can all be tracked to predict ovulation.

Commercial ovulation predictor kits, which contain home urine tests for lutienizing hormone (LH), are also available. Levels of lutienizing hormone rise (LH surge) in the 24-48 hours preceding ovulation, making it an accurate indicator of when ovulation will occur.

Estimates can be made of when the fertile window occurs for the "average" woman, based on average cycle length. Because women's cycles are highly individual and may vary from month to month, these estimates are likely less accurate than those made by observing changes to a woman's body.

Based on average estimates, the fertile window may be most likely to occur:

  • For women with cycles of 28 days, the fertile window may consist of days 12-14 of the cycle.
  • For women with cycles of 35 days, the fertile window may occur around days 19-21.
  • For women with cycles of 21 days, the fertile window may consist of days 5-7.

Women with cycles longer than 35 days or shorter than 21 day may not be ovulating regularly due to hormone imbalance, which may drastically decrease their ability to conceive. Such hormone imbalances can often be treated with the assistance of a fertility specialist.

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