Midrash for Chullin 141:19

כל שאינו מצורת אדם אינו ולד

For we have learnt: If a woman miscarried [and brought forth] something resembling cattle or a wild animal or a bird, whether it be a clean or unclean species, if it was a male she must observe<span class="x" onmousemove="('comment',' Cf. Lev. XII. On the birth of a male the mother must observe seven days of uncleanness and thirty-three days of purification, and on the birth of a female fourteen days of uncleanness and sixty-six days of purification.');">¹⁰</span>

Sifrei Devarim