Steroid metabolism by human chorion laeve from dichorionic twin pregnancies

Certain steroid metabolic properties of chorion laeve from dichorionic twin pregnancies were examined to determine whether they were present in chorion not contaminated by decidua or serum. In the chorion situated between the two amniotic sacs and not in contact with decidua, aryl sulfatase, 3 beta-hydroxysteroid dehydrogenase, and aromatase activities were found. This indicates that these reactions are present in chorion laeve and were not previously ascribed to this tissue because of decidual contamination. Specific cortisol binding was also present in this area of chorion laeve, which excludes serum contamination. It is suggested that the specific steroid-binding protein in the membranes may be derived from the transcortin-like protein present in amniotic fluid.