Hadith 501310
Chapter 2: Purity - كتاب الطهارة
حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عَائِشَةَ، زَوْجَ النَّبِيِّ صلى الله عليه وسلم قَالَتْ فِي الْمَرْأَةِ الْحَامِلِ تَرَى الدَّمَ أَنَّهَا تَدَعُ الصَّلاَةَ .
Yahya related to me from Malik that he had heard that A'isha, the wife of the Prophet, may Allah bless him and grant him peace, said that a pregnant woman who noticed bleeding left off from prayer.
Reference Muwatta Malik 501310
USC-MSA web (English) reference : Book 2, Hadith 102