PLACENTAL EXPRESSION OF ALPHA-SUBUNITS AND BETA-SUBUNITS OF HUMAN CHORIONIC-GONADOTROPIN IN EARLY PREGNANCIES WITH DOWNS-SYNDROME

This study examines the expression of alpha and beta subunits of human chorionic gonadotrophin (HCG) in samples of placental and decidual ti ssue obtained at 11-15 weeks of gestation from 30 control pregnancies and 11 pregnancies with trisomy 21. In the placental tissue, the conce ntrations of beta-HCG mRNA and alpha-HCG mRNA were augmented in six an d seven of the trisomy 21 cases respectively and in 16 and 14 of the c ontrol pregnancies. The median values of beta-HCG mRNA and alpha-HCG m RNA in the two groups were not significantly different. Although the m edian serum free beta-HCG concentration was significantly (P = 0.03) h igher in trisomy 21 pregnancies than the controls, there was no relati onship between serum free beta-HCG and relative abundance of beta-HCG mRNA in either the trisomy 21 pregnancies or the controls. Decidual ex pression of beta-HCG and alpha-HCG mRNA were below detection level in the Northern blot analysis in both the trisomy 21 pregnancies and the controls. These findings suggest that the increase in maternal serum f ree beta-HCG concentration in trisomy 21 pregnancies occurs during the post-transcriptional phase of HCG protein biosynthesis.