Litter size is a key determinant of the efficiency of pork production. In turn, placental function is a key determinant of whether an individual pig fetus survives during gestation and also influences piglet birth weights. Our previous results suggested that glucosamine supplementation during late gestation improved aspects of the structure of the placenta that likely affect placental efficiency, and also improved the number of live fetuses at 105 days of gestation, suggesting that it might be useful in improving litter size at farrowing. The objectives of this experiment were to further test the effect of glucosamine supplementation during late gestation on litter size and piglet birth weights. Sows (parity 2-8) were mated according to standard procedures and were treated with either 10 grams per day of glucosamine (128 sows) or glucose (127 sows) as a top dress on their feed from day 85 of gestation until farrowing. Total born, born alive, stillborn and mummies in the litter were recorded, and each piglet was weighed at birth and at weaning. Glucosamine supplementation increased total born by .4 piglets, born alive by .16 piglets, and increased stillborn piglets by .24 piglets. However, none of these overall differences were statistically significant. Birth weights were slightly greater in glucosamine (1.37 kg) compared to glucose (1.35 kg) supplemented sows and weaning weights were also slightly greater in glucosamine (5.48 kg) compared to glucose treated sows (5.43 kg). However, as with litter size results, these differences were not statistically significant. The incidence of stillbirth and preweaning mortality was numerically greater in glucosamine treated sows (9.9 and 16.7%, respectively) compared to glucose treated sows (8.4 and 16.0%, respectively), but once again these differences were not statistically different. However, the incidence of stillborn piglets was significantly greater in seventh and eight parity sows. We conclude that despite our previous results in gilts, glucosamine supplementation of sows from day 85 to farrowing did not improve litter size, birth weights or weaning weights, and increased stillbirth rate in late (7 and 8) parity sows.