Hadrat Ibn ‘Umar ra narrated that he divorced his wife while she was in the state of menses. Hadrat ‘Umar ra made mention of it to The Holy Prophet sas, and he sas said:
Command him to take her back, then divorce her when she is pure or she is pregnant.
(Sahih Muslim, Book 18, Hadith 8)
In commentary of 65:5 of the Holy Quran, the Promised Messiah as wrote:
The ‘iddat of divorce for pregnant women is that, until child- birth, after the divorce, they refrain from marrying again.
(Tafsir Hadrat Masih Mau‘ud, vol 8, p. 168)
In case of a divorce, Islam gives women greater rights to custody of children. From age 0–9, the mother has the primary right to custody of the child, and the father must pay child support during this time. From age 9–12, the father has the primary right to custody of the child, though if it is in the greater interest of the child, and the child so wishes, the mother can again be given custody. After the age of 12, the child can choose who to live with (Fiqh Ahmadiyya, vol. 2, p. 110–116).
In response to a woman who asked about custody, Hadrat Khalifatul-Masih IV rta said:
If someone has been deprived, it is man, not woman.
(Question Answer Session, May 17, 1984)
Islam does not allow men to divorce their wives during their menstruation when their attachment to them might be relatively less. A husband is permitted to divorce his wife when she is not menstruating or pregnant because he has more reason to try and reconcile differences.