1978 Volume 54 Issue 8 Pages 921-938
To study the relationship between maternal and fetal pituitary-adrenal axis, plasma concentrations of ACTH, cortisol, progesterone, and unconjugated estradiol and estriol were determined during late pregnancy and labor in women with normal and abnormal pregnancies. Plasma ACTH, progesterone, and unconjugated estradiol and estriol were determined by a radioimmunoassay technique. Unconjugated plasma cortisol was measured by a competitive protein binding method.
Results obtained were as follows :
(1) In 7 healthy women in the 10th month of pregnancy, the concentrations of plasma ACTH just before delivery were statistically higher than those found before the onset of labor. The fetal plasma ACTH concentration was much higher than the maternal level. No ACTH was detected in the cord plasma of two anencephalic infants.
(2) After ACTH infusion into 4 healthy women during labor, the concentrations of ACTH in their plasma increased to about 2.2 to 10.4 times the control values, while the concentrations in the cord plasma of their newborn infants decreased significantly. The difference between the ACTH concentrations in infants delivered from normal women and from women infused with ACTH was significant.
(3) In 6 healthy women, the concentrations of plasma cortisol just before delivery were statistically higher than the levels found before the onset of labor, and the fetal plasma cortisol level was significantly lower than the maternal level. In two women with anencephalic fetuses, the maternal plasma concentrations of cortisol were similar to those in six women with normal fetuses, while the cortisol concentrations in the cord blood were significantly lower than those in normal newborn infants.
(4) After ACTH infusion into 4 healthy women during labor, the concentrations of cortisol in their plasma increased slightly, but not significantly.
(5) In 7 healthy women, the concentrations of plasma estradiol and estriol during labor did not change, and the fetal plasma estradiol and estriol concentrations were significantly higher than the maternal levels. In three women with anencephalic fetuses, the maternal plasma concentrations of estradiol and estriol during labor were very low. It is interesting that estradiol concentrations in the cord blood of two of these fetuses were similar to those of their mothers, while estriol concentrations were higher than those of the mothers.
(6) After ACTH infusion into 4 healthy women during labor, the concentrations of estradiol and estriol in their plasma did not differ from the control values, while the levels of estradiol and estriol in the cord plasma of the newborn infants were significantly lower than those normally found in newborn infants.
(7) There were no differences among the plasma progesterone concentrations during labor in normal pregnant women, in normal pregnant women with ACTH infusion and in pregnant women with anencephalic fetuses or between those in normal newborn infants and those in anencephalic infants.
(8) ACTH was infused for 3 hr into 10 pregnant women beyond term by ten days or more. The concentrations of plasma estradiol and estriol in all the patients did not change for 2 hr following ACTH infusion, but definitely decreased 3 hr after the cessation of ACTH infusion, following a rise of the plasma cortisol levels.
These results obtained suggest that ACTH does not cross the placental barrier, that during late pregnancy and labor the maternal adrenal cortex responds rapidly to infused ACTH by increasing corticosteroids synthesis, and the corticosteroids cross the placental barrier from the maternal to the fetal side and suppress fetal adrenal secretion, and so decrease production of estrogen precursor in the fetal adrenal, resulting in lowered estrogen levels of fetal plasma, and that as far as the progesterone is concerned, the human placenta is a unique site of synthesis and this synthesis is under self-control.
