ACTH levels in amniotic fluid during pregnancy.

The fetal pituitary-adrenal axis plays an important role in the role in the regulation of fetal development. In order to obtain information about fetal ACTH secretion at different gestational ages, a total of 109 amniotic fluid ACTH determinations was performed by radioimmunoassay. There was a significantly higher level of ACTH during 26 to 30 weeks of pregnancy (429 +/- 180-4 pg/ml) than in early (208-7 +/- 90-6 pg/ml) and in late (172-7 +/- 97-4 pg/ml) pregnancy; fetal sex, uterine contractions and maternal complications in pregnancy did not affect levels. The ACTH level in the first urine of six newborn infants (160-0 +/- 40-6 pg/ml) approximated to that in the amniotic fluid in late pregnancy. Our results support the assumption of a fetal origin for ACTH in amniotic fluid. The high secretion of ACTH at the beginning of the last trimester of pregnancy may stimulate the development of the adrenal cortex and result in the increased cortisol secretion necessary for fetal lung maturation.