Does a miscarriage terminate iddah?
The answer
In principle, a pregnant woman’s iddah (waiting period) is the duration of pregnancy until delivery.
Depends on: Whether the foetus's limbs were partially formed.
Explanation
If a woman experiences a miscarriage, the state of the foetus will determine whether the iddah has expired or not. If the foetus’ limbs were partially formed, then the iddah will expire due to such a miscarriage.
If the foetus was not formed at all, the woman will have to complete the waiting period otherwise. Namely, three menstruation cycles, three months or 4 months and 10 days in the event of death.1
And Allah knows best.
Mufti Faraz Adam
References
1وَشَرْطُ انْقِضَاءِ هَذِهِ الْعِدَّةِ أَنْ يَكُونَ مَا وَضَعَتْ قَدْ اسْتَبَانَ خَلْقُهُ، فَإِنْ لَمْ يَسْتَبِنْ خَلْقُهُ رَأْسًا بِأَنْ أَسْقَطَتْ عَلَقَةً أَوْ مُضْغَةً لَمْ تَنْقَضِ الْعِدَّةُ كَذَا فِي الْبَدَائِعِ. (الهندية ج 1 ص 529 الرشيدية)
إِذَا أَسْقَطَتْ سِقْطًا إنْ اسْتَبَانَ بَعْضُ خَلْقِهِ انْقَضَتْ بِهِ الْعِدَّةُ لِأَنَّهُ وُلِدَ وَإِلَّا فَلَا (حاشية ابن عابدين ج 3 ص 512 أيج أيم سعيد)
Based on the Hanafi school and on the question as it was asked. Another mufti may reach a different conclusion. Read the disclaimer.