Twenty-four swine commercial farms participating regularly in a swine performance monitoring project were utilized to compare the reproductive performance of small (mean=133 sow level), medium (mean=331 sow level) and large (mean=1295 sow level) farms. The effects of farm sizes, quarter, months nested within quarter and farm sizes by quarter interactions were analyzed. The small farms obtained significantly higher total pigs born, but were offset by significantly higher percent mummified and stillbirth. The reproductive indices such as weaning to conception interval, farrowing index, farrowing interval and nonproductive days of large farms were significantly better than the small and medium size farms. The farrowing rate, farrowing index, nonproductive day and farrowing interval were worst in the months of August and September. The percent mummified fetuses, stillbirths, weaning mortality, farrowing interval, incidence of abortion and nonproductive days were significantly higher, while the litter size born alive, litter size at weaning, percent born alive, farrowing rate and pigs weaned/sow/year were significantly lower on the third quarter, hence the third reproductive syndrome. This syndrome may be attributed to photoperiodic sensitivity, feed contaminated by aflatoxin and environmental stress affecting feed intake and the reproductive functions.