Midrash for Bekhorot 91:17
מי שלא היו לו בנים ונשא אשה שכבר ילדה
HAVING AN ARTICULATED SHAPE, OR IF AN EMBRYO CAME OUT BY PIECES,<span class="x" onmousemove="('comment',' Limb by limb, but since the whole came forth, it is regarded as an opening of the womb. But if the head of the infant alone came forth by pieces, this is not considered an opening of the womb if its companion came forth afterwards before the majority of the limbs and pieces managed to emerge, and the latter offspring is regarded also as a first-born to be redeemed from a priest.');"><sup>13</sup></span>
Sifrei Devarim
"… over the face of the son of the hated one": We are hereby taught that if his head or most of it emerged live (from the womb), he negates the next birth as a first-born.
Ask RabbiBookmarkShareCopy