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

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Onot after period induced with Prometrium

30 March, 2006


I went off of birth control back in September, had my period three times and then it stopped. It has now been 3 months since my last period and my doctor has put me on prometrium to induce my period. My question is after this induced period how do I treat the different onot, specifically the interval. Should I be calculating an interval onah from 3 months ago or should I use what I had prior, or not have an interval onah. The doctor did say that they would continually put me on the medication about every two months to try and help us conceive.


In this case, where a full three months have elapsed since your prior onot and the period will be brought on by medication, all prior onot are moot.  After menstruating this cycle, you will observe the day of the month and the thirty-day interval.  After the second upcoming cycle, you will have a new interval to observe.  If you menstruate three times induced by Prometrium (a form of progesterone), you will then observe the interval between taking the Prometrium and the onset of menstruation in any future induced cycles.  In that case, you would cease to observe the day of the month, thirty-day interval, or interval day.

We wish you success with your efforts to conceive. If you’d like to speak further about fertility and halacha, click here to arrange for a free consultation with a Yoetzet Halacha Fertility Counselor.

Please write back with any further questions.

This response was updated on 26 August, 2021.

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