Is it necessary for a woman to wait for the call of Azan before she can offer her prayers (salah) or can she perform her prayers as soon as the time for that particular prayer becomes due?
The ladies need not wait for the call of Azan. They can offer their prayers soon after they are sure that the time for a particular salah has arrived, no matter whether the call of Azan has been pronounced in the musjid or not.
The Holy Qur’an says:
إن الصلوۃ کانت علی المؤمنین کتابا موقوتا
Surely, the Salah for the Muslims is an obligation related with time.
It is clear from this verse of the Holy Qur’an that the basic requirement for the validity of a particular salah is that it should be performed within the time prescribed for it.
The call of Azan, on the other hand, is meant for inviting men to proceed to the masjid for their congregational prayer. Since women are exempt from joining the congregational prayers, they are not concerned with the call of Azan. They can offer their prayers in their homes well before Azan, provided the prescribed time has arrived. The only thing they are required to do is to make sure that the prescribed time has come.
Source: Contemporary Fataawa, By Mufti Muhammad Taqi Usmani