Is 'iddah obligatory for a woman who sought khulʿ from her husband after losing her fetus in the fifth month, and when does its calculation begin?

The timing of the divorce is not clear. If it occurred before childbirth, your waiting period (iddah) ended with the delivery, based on the verse: "And for those who are pregnant, their term is until they deliver their burden." [Quran 65:4]. If the divorce occurred after childbirth, your waiting period is three menstrual cycles, starting from the day of the divorce, based on the verse: "Divorced women shall wait concerning themselves for three courses." [Quran 2:228]. It is advisable to be deliberate in choosing spouses and to consult trustworthy individuals.