Form and development of the umbilical cord in pigs and their association with delivery of viable pigs.

Length, extensibility, and absolute strength of umbilical cords were determined in litters of pigs at term. Length was also determined in fetuses earlier in gestation and in hypophysectomized fetuses. Mean cord length at term was 34.6 cm (range, 17 to 50 cm) and its length was correlated with length and birth weight of pigs. Cords were significantly (P less than 0.01) shorter in hypophysectomized fetuses, but cord length was not influenced by sex, position in the uterus, or twisting of the cord. Although the umbilical cord was capable of being stretched considerably, the degree varied among pigs. Tension required to break portions of the cord ranged from 545 to 2,000 g. Variations in length, elasticity, and strength of the cord may influence safe delivery, birth asphyxiation, and perinatal mortality in pigs.