Numbers of total (P ≤ 0.001), live-born (P ≤ 0.001), and stillborn piglets (P = 0.010) were greater in sows than in gilts (Table 1). Numbers of mummified piglets tended to be greater in sow litters than in gilt litters (P = 0.062), were greater in litters from dams treated with pST from d 25 to 50 of pregnancy (P = 0.014) than in controls, and were not altered in litters from dams that were treated with pST from d 25 to 100 of pregnancy (P = 0.146). Total piglet numbers were less in litters from dams treated with pST from d 25 to 100 than in controls (P = 0.038), and were not reduced in litters from dams treated with pST from d 25 to 50 of pregnancy (P = 0.166). Numbers of stillborn piglets tended to be increased in litters from dams treated with pST from d 25 to 50 compared with controls (P = 0.079) and were not altered in litters from dams treated with pST from d 25 to 100 of pregnancy (P > 0.9). Consequently, the numbers of live-born piglets in each litter were reduced by approximately 0.6 piglets/litter after pST treatment, either from d 25 to 50 of pregnancy (P = 0.018) or from d 25 to 100 of pregnancy (P = 0.024), compared with control litters (Table 1)