Effect of Stage of Gestation, Litter Size and Uterine Space on the Incidence of Mummified Fetuses in Pigs

: Factors associated with incidence of mummified fetuses at 7, 9, 11, 13 and 15 wk of gestation were determined in a cross-sectional design involving 209 pregnant pigs. Percentage of observed mummies increased from 2.1 to 12.2% as gestation progressed. Incidence of mummies at 7 wk of gestation was not different between litters of nine fetuses or fewer and those of 10 fetuses or more. During the period of 7 to 15 wk of gestation, the incidence of mummies remained constant at about 1% in litters of nine fetuses or fewer, whereas in litters of 10 fetuses or more the incidence increased linearly from 1 to 12% (P less than .01). In litters of nine fetuses or fewer, a mummy occupied no less space than a live fetus until 13 wk of gestation. In litters of 10 fetuses or more, a mummy occupied less space than did a live fetus after 7 wk of gestation. An increase in the incidence of mummies in larger litters was associated with uterine space per fetus below that needed for development and survival. The 12% fetal loss in late gestation was associated with less uterine space per fetus. Length of uterine horns, litter size and stage of gestation together accounted for 12% of the variation in incidence of mummies (P less than .001). A longer uterus had greater space per fetus, a larger number of live fetuses and a lower incidence of mummies.