During gestation piglets orient themselves at random. About 1/2 are born head first and 1/2 are born tail first. Sometimes piglets will be born 1 or 2 from one horn and then 1 or 2 from the other or sometimes one horn is emptied and then the other. Again it is random. See the Purdue Porkpage for more information on farrowing. (we will put a link here)
Piglets located near the cervical end tend to be heavier at birth.
Males are heavier at birth than females.