Nishmat's Women’s Health and HalachaIn memory of Chaya Mirel bat R' Avraham

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I track ovulation. Do I need to keep yom hachodesh & onah beinonit?

4 January, 2023


Do I need to observe day 30/31 if I tracked my ovulation and know my period is not expected in these days?


Thank you for reaching out to us.

If you have consistently tracked your ovulation for at least three months in a row, so that you have established a minimum interval between ovulation and the onset of flow, then this has halachic weight. If the day of the month and onah beinonit occur before the earliest time you would expect your period based on ovulation, you are exempt from observing them.

Also, we follow the view that a woman whose flow consistently (three times consecutively) begins after day 31 of her cycle need not observe the onah beinonit or day of the month, but only the interval. If this is true in your case, then you will not need to observe those days for as long as this pattern persists.

We hope that this is clear. Please be in touch with any further questions.

This internet service does not preclude, override or replace the psak of any rabbinical authority. It is the responsibility of the questioner to inform us of any previous consultation or ruling. As even slight variation in circumstances may have Halachic consequences, views expressed concerning one case may not be applied to other, seemingly similar cases. All health and health-related information contained within Nishmat's Women's Health & Halacha Web site is intended to be general in nature and should not be used as a substitute for consulting with your health care professional. The advice is intended to offer a basis for individuals to discuss their medical condition with their health care provider but not individual advice. Although every effort is made to ensure that the material within Nishmat's Women's Health & Halacha Web site is accurate and timely, it is provided for the convenience of the Web site user but should not be considered official. Advice for actual medical practice should be obtained from a licensed health care professional.

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