Uterine position and presentation of minipig-fetuses and their order and presentation at birth

Uterine position and presentation of fetuses in 17 minipigs during pregnancy were compared with their order and presentation at birth. Fetuses from 1 or both uterine horns were marked between day 80 and day 105 of gestation by 1 or more transuterine injections of either a 2.5% solution of dianil blue (3 animals) or a radiopaque substance (14 animals). Roentgenograms of the newborn pigs, which were ear-notched immediately after birth, enabled making individual identification. Pigs seemed to be delivered randomly from the 2 uterine horns. They either followed a neighbor from the same horn (n = 42) or followed a pig from the contralateral horn (n = 52). Only in 3 dams did 1 uterine horn become empty before delivery from the other horn started. In 4 dams, 1 pig passed its neighbor from the same horn, thereby being born earlier than expected. Moreover, passing of pigs could have occurred and gone undetected in those dams from which the pigs of only 1 horn were marked. This passing might have taken place within the uterine body. From 18 of 95 pigs (19%) , the presentation at birth differed from the one observed at laparotomy.