Gestation age dependent transfer of human immunoglobulins across placenta in timed-pregnant guinea pigs.

•G. pigs transfer human IgG transplacentally during the third trimester at higher levels than at earlier time-points.•Both the average fetal concentration and fetal:maternal ratio of human IgG increase in the third trimester.•In vitro assays with g. pig FcR recapitulate human IgG binding and its internalization by epithelial cells.•More studies are needed to fully understand FcRn mediated placental transport.