After that Umar agreed with Ubayy bin Kab and said...
After that Umar agreed with Ubayy bin Kab and said: If she had given birth to her child and her husband was still not buried yet, she could get married.[2] The followers of the four Sunni sects have followed this principle until nowadays.
But we, the Shia, have found in the holy Qur'an two verses opposing each other concerning the iddah of a woman whose husband dies while she is pregnant; in the first verse Allah has said: and (as for) the pregnant women, their prescribed time is that they lay down their burden. Qur'an, 65:4 and in the second one He has said: And (as for) those of you who die and leave wives behind, they should keep themselves in waiting for four months and ten days.
Qur'an, 65:4 A pregnant woman, whose husband dies, can get married after giving birth to her child if she follows the first verse even if she has not passed the period of iddah mentioned in the second verse but if she follows the second verse, she can get married only after passing the period mentioned in the verse even if she has not given birth to her child yet.
In both suppositions she will objects to one of the verses and she cannot follow both of the verses at the same time unless she will wait until passing the longer of the two periods (either to pass four months and ten days or until giving birth to her baby) and then she has no way except to do that. This is what has been narrated from Imam Ali (s) and ibn Abbas.[3] The Shia have followed their imams in acting according to this opinion.
[3] Mentioned by az-Zamakhshari in his Kashshaf when interpreting this verse (and (as for) the pregnant women, their prescribed time is that they lay down their burden). This is the opinion of Ahlul Bayt (s) and it is the most cautious opinion. [4] When a wifes husband dies. from her or because of any other reason. As for the Shia, they believe that the iddah of death begins when a wife knows of her husbands death even if the death has taken place some time ago.