Major losses of body weight and fat reserves during the first lactation are a cause of unsatisfying reproductiveperformances in primiparous sows. This study, conducted in three commercial sow herds, investigatedwhether weaning the sows three days earlier together with administering altrenogest was effectivefor improving reproductive performance (weaning-to-estrus interval, pregnancy rate after firstinsemination, total litter size and number of live born piglets in the second litter) and body condition. Inthe herds suffering from the second litter syndrome, a non-significant improvement of the second litter sizewas found with on average 1.9 extra piglets born. During the treatment period, the treated sows gainedon average 1.4 mm back fat, while the control sows lost 0.4 mm back fat. In conclusion, the treatment isuseful for putting the sows in better condition at the moment of insemination and it may possibly improvereproductive performance in farms with the second litter syndrome.