There seems to be an optimal value for birth weight with regard to calf viability (Meijering, 1984). Koots et al. (1994b) reported positive genetic correlations between birth weight and perinatal mortality, suggesting that in most studies, birth weight was larger than optimum. Calving difficulty and stillbirth generally have higher incidences in the first parity vs. later parities and have been suggested in some studies to be genetically different, but correlated, traits in first and second-parity cows (Weller et al., 1988; Luo et al., 2002; Steinbock et al., 2003). This information is needed to review genetic parameters via evaluate whether more direct measures of calving difficulty and birth weight should be considered in the genetic evaluation based on field data.