What is the waiting period (iddah) for a divorced woman who menstruates every two months or every month and a half?

The waiting period (iddah) for a divorced woman who menstruates does not end except after three complete menstrual cycles, based on the Almighty's saying: (Divorced women remain in waiting for three menstrual cycles) [Al-Baqarah: 228]. It is not permissible to deviate from this to observe the iddah in months, except in cases of despairing of menstruation or not having reached the age of menstruation, based on the Almighty's saying: (And those of your women who have despaired of menstruation – if you have doubts – then their waiting period is three months, and also those who have not menstruated) [At-Talaq: 4]. So, the iddah is by menstruation for those who have menstrual cycles, and by months for those who have despaired and for the young.