Risk factors for retained placenta in the cow: A retrospective study in the North West of Spain Risk factors for retained placenta, considered as such when it had not been expelled after 24 h post partum, were studied using 1951 cows, and the same number of calvings, from 79 farms sited in the province of Lugo (Galicia, North West of Spain). Data were obtained from previous records collected by veterinarians or farmers. Potential risk factors considered in this study were: farm size and localization, calving season, breed type, parity, pregnancy length, calving difficulty, twin calves and hypocalcaemia disease. The mean incidence of retained placenta was 6,6%. Multiple logistic regression analysis indicated that twin calves (odds ratio: OR=2,53, p<0,01), dystocia (OR=2,28, p<0,05) or in cow belonging to farms located in the central area of the province (OR=2,23, p<0,01) were risk factors for retained placenta. However, an increased pregnancy length (OR=0,96, p<0,01) was associated to a low risk for retained placenta.