Vestot When I Know Ovulation

I am undergoing various fertility treatments, and as part of the treatment they tested exactly when the ovulation was. Based on that, I know relatively accurately when my period will come. Do I have to keep all the regular vestot, being that it seems pretty unlikely that the period will actually come on those days.

You should keep all vestot like regular. Since Chazal instituted that one must keep vestot, we don’t find anywhere that outside knowledge about when the period might come can affect the calculation of these vestot. In addition, calculating when the period will arive based on ovulation is not perfectly accurate, and therefore cannot be used to be lenient in vestot.

We only find a מסולקת דמים doesn’t have to keep vestot. Even pregnancy in the first 3 months and birth control pills which prevent periods are a discussion in the poskim if one can be lenient in such cases. But in both these cases, we have something that we know prevents a period from coming, but here where we are just calculating when the period will come it is much worse since we know it is coming and we are just trying to calculate when.

פתחי דעת פל”ח סעי’ יח

Rabbi Shay Tahan