Cortisol binding capacity and oestrogen concentrations in maternal and cord plasma in pregnancies with normal and anencephalic fetuses.

The cortisol binding capacity of maternal and cord plasma samples obtained at delivery from fifteen women and their normal infants and from seven women and their anencephalic infants was measured at 4 degrees C by a gel filtration technique. The concentration of oestrogen in these samples was measured by radioimmunoassay. There was no significant difference (t test) between the cortisol binding capacity of peripheral plasma from women with normal infants (1-55 +/- 0-24 mumol/1, mean +/- SD) and from those who delivered anencephalic infants (1-35 +/- 0-30 mumol/1), nor between the cortisol binding capacity of cord plasma from anencephalic infants (0-47 +/- 0-04 mumol/1) and that of normal infants (0-37 +/- 0-10 mumol/1). However, mean oestrogen concentrations in maternal and cord plasma from the pregnancies with an anencephalic fetus were significantly lower (P less than 0-01) than in the corresponding samples from normal pregnancy. It is concluded that oestrogen concentrations in maternal and cord plasma in normal pregnancy at delivery are much greater than those required to account for the increase in plasma cortisol binding capacity. Since plasma cortisol binding capacity in pregnancy with an anencephalic fetus is not diminished, the reduced excretion of corticosteroids relative to normal pregnancy in this condition is unlikely to be due to alterations in cortisol metabolism associated with a lower plasma cortisol binding capacity.