In  commercial hog barns sows during early and mid gestation experience spontaneous fetal loss reaching 30-45%. It is not clear why these losses occur but poor blood supply to the developing conceptus is suspected to be the cause. This study documented that  type 1 cytokines dominate early pregnancy, while type 2 cytokines are more common after mid-gestation. Type 1 cytockines were more common at arresting conceptus attachment sites comapred to healthy ones. It was also noted that chemokines and their decoy receptor was significantly higher in arresting sites at mid-gesstation.  Using an intra-uterine infusion of MCC (Bioniche life sciences, Inc.), litter size was increased by 3 piglets in treated sows compared with control. Runts were very rare in treated compared with placebo animals. Other effects of MCC include stimulation of maternal fetal vasculature and numbers and size of corpora lutea. Overall this proposal made significant advances towards the understanding of embryo loss during porcine pregnancy and therapeutic promotion of litter size.