Waleed bin Muslim narrates: I said to Imam Malik: I have been told regarding Sayyida Aisha (may Allah be pleased with her) that she said: "A woman can be pregnant for up to two years, as long as the shadow of a spindle." So Imam Malik said: "Subhan Allah! How can anyone say such a thing? This girl of ours, who is the wife of Muhammad bin Ajlan, she is a pious woman, and her husband is also a pious man. She has given birth to three children in twelve years, each of whom remained in their mother's womb for four years."
Hadith Referenceسنن الدارقطني / كتاب النكاح / 3877