Maliks Muwatta Book 23, Hadith Number 13.

Section : The Sacrificial Animal for the Child in the Womb and Mention of the Days of Sacrifice.

Yahya related to me from Malik from Nafi that Abdullah ibn Umar did not sacrifice for the child in the womb.

Malik said, “The sacrifice is sunna, and it is not obligatory. I prefer that anyone who has the price of the animal should not abandon it.”