It is narrated from Sayyida Umm Karz (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) said regarding ‘Aqiqah: “For a boy, two goats are to be sacrificed, and for a girl, one goat is sufficient.”
Hadith Referenceسنن دارمي / من كتاب الاضاحي / 2005
The sacrifice performed on the seventh day after the birth of a newborn boy or girl is called ‘aqiqah, which is Sunnah on the seventh day. Some scholars have declared it obligatory, while others have considered it recommended (mustahabb); the first opinion is more correct, as is mentioned in the referenced hadith. It is Sunnah to slaughter two goats for a boy and one goat for a girl; in case of necessity, one goat may also be slaughtered for a boy. The Sunnah method is to avoid ostentation, showing off, extravagance, and wastefulness in this matter, so that this Sunnah does not become a burden instead of a mercy.
Imam Shafi‘i rahimahullah has stipulated, as in the case of the (Eid) sacrifice (udhiyah), that the animal for ‘aqiqah must be free of defects. He has also stated that camels, cows, etc., may also be slaughtered for ‘aqiqah.