بسم الله الرحمن الرحيم
(Fatwa: 1122/868/D=10/1434)
If a Muslim doctor suggests that the fast shall be harmful for the woman then in such case she is allowed to miss the fast. And later when the days are shorter she should make its qadha. Only qadha is enough.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband
