Which Surah is referred to as "the Middle Surah of Women"?

There is no Sura in the Holy Quran called "Surat An-Nisa Al-Wusta" (The Middle Women), unless it is used metaphorically. An account from Ibn Mas'ud suggests the existence of "An-Nisa At-Tuwla" (The Longer Women) and "An-Nisa Al-Qusra" (The Shorter Women) in the context of the waiting period (iddah) for a widow. By "Al-Qusra," he meant Surat At-Talaq ("And whoever fears Allah – He will make for him a way out"). By "At-Tuwla," he meant Surat Al-Baqarah ("And those of you who die and leave wives behind them, they shall wait (as regards themselves) four months and ten (days)"). Ibn Mas'ud's intention was not to name the Surahs, but rather the verses related to the iddah. The naming of Surahs is divinely ordained (tawqifi) and depends on what has been heard and transmitted.