Overall, semen backflow was observed in none, one, and more than one insemination in 72.4% (432/597), 22.1% (132/597), and 5.5% (33/597) of the sows, respectively. The FTPCAI1 sows with semen backflow in one AI and the MultPCAI sows with semen backflow in at least two AIs had lower odds of farrowing (P < 0.05) compared with sows without semen backflow. However, the occurrence of backflow during insemination had no influence on farrowing rate (P > 0.05) in FTPCAI2 sows (Table 3). The presence of backflow in the single AI performed in FTPCAI1 sows reduced their litter size (Table 3), whereas a smaller litter size was observed in MultPCAI sows when backflow was present in at least two inseminations (P < 0.05).