We are sorry to hear of your miscarriage.

Assuming that you did not have an established veset (veset kavua) before your pregnancy, you are halachically considered to have no previous cycle history. You have no onot perishah to observe until you start menstruating again. An entirely new pattern will be established after the miscarriage.

First, you need to stop bleeding, complete the taharah process and use the mikveh. Just as after childbirth, this may take a few weeks and the bleeding may be somewhat “on and off.” For more on the laws of mikveh following a miscarriage, please see our article on Pregnancy Loss.

From your first period after mikveh immersion, you calculate the date of the month (chodesh) and thirty days (beinonit) for the next month. You will not yet have an interval. After your second period, you calculate the chodesh, the thirty days, and the interval that you just experienced. It is not unusual for the cycles to be a bit irregular for a few months as the body resets itself to regular cycling.

Note: This answer follows the halachic position of our Rabbinic Supervisors, that pregnancy resets a woman’s veset calendar from the point that it is medically confirmed (e.g., through a positive pregnancy test). Some other authorities follow the view that, if a miscarriage occurs within forty days of a woman’s pre-pregnancy immersion, she observes all of her usual onot perishah.

This response was updated on 23 February, 2023.