By Allah, I am ready to invoke Allah's curse with whoever wishes to dispute me. The shorter Surah of Women was revealed specifying four months and ten days.
حدثنا محمد بن المثنى حدثنا أبو معاوية عن الأعمش عن مسلم عن مسروق
والله لمن شاء لاعناه لأنزلت سورة النساء القصرى بعد أربعة أشهر وعشرا
Sourcing, [sahih] Abu Dawud narrated it in the Book of Divorce, Chapter on the Waiting Period of a Pregnant Woman, no. 2307, from the hadith of Abu Muawiya, with this wording. See no. 178 for its ambiguity. The hadith has many paths of transmission, but they are flawed due to the tadlis of the narrators, and the rest is sahih by corroborating evidence.