Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Abdullah that the Holy Prophet (peace and blessings be upon him) conducted li'an between a man and his wife and said, "It is hoped that a dark-skinned child will be born to this woman." So, a dark-skinned child was born to that woman.

Hazrat Ibn Abbas (may Allah be pleased with them) narrates that the Noble Prophet (peace and blessings be upon him) conducted li'an on the basis of pregnancy.

This fatwa is narrated from Hazrat Sha'bi regarding the man who disassociates himself from his wife's pregnancy, that such a man will perform li'an (mutual cursing) with the woman. And (Imam) Abu Hanifa's opinion is mentioned that: he did not consider li'an to be established on the basis of denial of pregnancy.