"Whoever wants, I will meet and debate with him and invoke the curse of Allah upon those who lie. The Verse: 'And for those who are pregnant (whether they are divorced or their husbands are dead), their 'Iddah (prescribed period) is until they lay down their burden.' was only revealed after the Verse about women whose husbands die. 'When a woman whose husband has died gives birth, it becomes permissible for her to marry.'" This is the wording of Maimun (one of the narrators).  

مَنْ شَاءَ لاَعَنْتُهُ مَا أُنْزِلَتْ { وَأُولاَتُ الأَحْمَالِ أَجَلُهُنَّ أَنْ يَضَعْنَ حَمْلَهُنَّ } إِلاَّ بَعْدَ آيَةِ الْمُتَوَفَّى عَنْهَا زَوْجُهَا إِذَا وَضَعَتِ الْمُتَوَفَّى عَنْهَا زَوْجُهَا فَقَدْ حَلَّتْ وَاللَّفْظُ لِمَيْمُونٍ  

[Machine] That they (widows) should wait [for] their waiting period. But if you fear that they will not be able to maintain [the limits of] Allah, then there is no blame upon them for what he ransoms her thereby. These are the limits of Allah, so do not transgress them. And whoever transgresses the limits of Allah, it is those who are the wrongdoers.

And those who are taken in death among you and leave wives behind - they, [the wives, shall] wait four months and ten [days].  

أَنْ يَضَعْنَ حَمْلَهُنَّ} [الطلاق 4] إِلَّا بَعْدَ آيَةِ الْمُتَوَفَّى عَنْهَا زَوْجُهَا إِذَا وَضَعَتِ الْمُتَوَفَّى عَنْهَا زَوْجُهَا فَقَدْ حَلَّتْ يُرِيدُ بِآيَةِ الْمُتَوَفَّى عَنْهَا زَوْجُهَا {وَالَّذِينَ يُتَوَفَّوْنَ مِنْكُمْ وَيَذَرُونَ أَزْوَاجًا يَتَرَبَّصْنَ بِأَنْفُسِهِنَّ أَرْبَعَةَ أَشْهُرٍ وَعَشْرًا} [البقرة 234]