Alterations in human placental 11beta-hydroxysteroid dehydrogenase type 1 and 2 with gestational age and labour.

11beta-hydroxysteroid dehydrogenase type 1 and type 2 may be important in the process of human parturition and the regulation of fetal growth, by the modulation of cortisol concentrations in the fetal compartment. Changes in the expression and activity of these enzymes in late gestation have not been well described. This study has examined the gene expression of placental 11beta-HSD1 and 2, activity of 11beta-HSD2 and fetal cortisol concentrations during the final few weeks of human pregnancy and with the onset of labour. Placental 11beta-HSD2 activity decreased significantly between 38 and 40 weeks. There were no significant changes in mRNA abundance or protein expression with gestational age or labour. Placental 11beta-HSD1 mRNA abundance significantly increased with spontaneous labour. Fetal cortisol concentrations increased significantly with spontaneous labour. This study is the first to describe a decrease in 11beta-HSD2 activity in the last few weeks of human gestation. This decrease in type 2 activity, along with an increase in 11beta-HSD1 gene expression may be a mechanism by which cortisol concentrations rise at term to regulate fetal maturation and activate pathways associated with labour.