Calculating date of conception

Hello,
I had a miscarriage four days ago. The interval from my last mikvah immersion until the miscarriage was 75 days. Does the 40–day cutoff for yoledet status depend simply on the date of immersion (i.e. do we just assume that that was the date of conception), or is other medical evidence taken into account in determining whether the miscarriage was 40 days from conception? My periods are irregular, and ovulation unpredictable. I had three ultrasounds over three weeks, none of which showed any signs of life; there was only a gestational sac. Moreover, the gestational sac was small, so the doctor estimated that my date of conception was several weeks later than the day I went to mikvah. Do I need to wait 12 days or 14?
Thank you so much for your help.

Dear questioner,

Thank you for your question.

We are sorry to hear of your miscarriage.

With respect to this halacha, we are stringent in cases of doubt.  The yoledet status depends on the interval from the date of the first act of relations after immersion (in most cases, the same date as immersion) to the date of the miscarriage (even where signs of life were not detected earlier).  Therefore, you should indeed wait fourteen days prior to immersion.

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.

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