The mechanism for decreased insulin sensitivity in pregnant women is not fully clarified. Resistin, a novel peptide hormone, is specifically expressed in the adipose tissue and decreases insulin sensitivity in rodents. In the present study, we demonstrate resistin gene expression in the human placental tissue, mainly in trophoblastic cells. The resistin gene expression in term placental tissue was more prominent than was seen in the first trimester chorionic tissue. In contrast resistin gene expression in adipose tissue was rather weak and remained unchanged by pregnancy. Thus, resistin is a newly isolated placental hormone in humans which may modulate insulin sensitivity during pregnancy.