It is narrated from Sayyidah Umm Kurz (may Allah be pleased with her) that she asked the Messenger of Allah (peace and blessings be upon him) about the aqiqah. He (peace and blessings be upon him) said: "For a boy, two sheep, and for a girl, one sheep, and it does not harm you whether they are male or female."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21867