The moment the husband passed away, her iddat began. If she is not pregnant then her iddat will be for 4months and 10 days. If she is pregnant then her iddat will only be completed after the child is born. [Fatawa Raheemiya, vol. 7/8, page 433-35
It is stated in the Quran: ?And those of you who die and leave wives behind them, they (the wives) shall wait (as regards their marriage) for four months and ten days, then when they have fulfilled their term, there is no sin on you if they (the wives) dispose of themselves in a just and honourable manner (i.e. they can marry). And Allah is Well-Acquainted with what you do.? [surah baqarah ayat 234]
It is also stated in the Holy Quran: ?and those of your women as have passed the age of monthly courses, for them the iddah (prescribed period), if you have doubt (about their periods), is three months; and for those who have no courses [(i.e. they are still immature) their iddah is three months likewise, except in the case of death]. And for those who are pregnant (whether they are divorced or their husbands are dead), their iddah is until they lay down their burden; and whosoever fears Allah and keeps his duty to Him, He will make his matter easy for him.
If the husband dies on the day of a crescent [(the beginning of a new moon), then according to the moon (29th, or 30th moon)] she can complete her four months and ten days according to lunar calculation.
However if he does not die on the day of the crescent, then the Iddat will be 130 days. (durr muktar and shami page 829, baab-ul-iddat bahishti zewar page 85, vol.4, maut ki iddat ka bayan)
[fatawa Raheemiya page 433-35, vol 7/8]
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai