Genetic parameters including the proportion of variance for the service sire effect were estimated for number of piglets stillborn (including piglets died until 24 h after birth) and number of piglets died from 24 h after birth until weaning in Czech Large White (89 231 litters) and Czech Landrace (28 320 litters) pigs. Both traits were considered to be traits of the sow. The heritability for number of stillborn piglets was 0.06 in both breeds and the heritability for number of piglets died until weaning was 0.07 in Czech Large White and 0.05 in Czech Landrace. The proportion of variance due to service sire was very low (between 0.8 and 1.6%). A selection against farrowing losses is recommended though only a slow improvement of the trait can be expected. Selecting against piglets died until weaning seems to be cumbersome. Probably a selection on number of piglets weaned could be helpful not further to increase piglet losses until weaning.