Musannaf Ibn Abi Shayba 13:749

Abu Bakr narrated to us, he said: Isa ibn Yunus narrated to us, from al-Awza’i, from al-Zuhri, who said: The Sunnah has passed that the testimony of women is permissible in matters which no one else can observe, such as the births of women and their physical defects. And the testimony of the midwife alone is permissible regarding the crying (of a newborn), and two women (are required) in matters other than that.