Adrenocorticotrophic hormone during the first day of life.

The plasma concentration of ACTH (by radioimmunoassay) was measured in 56 healthy parturients and their newborns. Umbilical cord and maternal venous blood were collected immediately after delivery. In addition one venous blood sample was taken from 50 newborns at the age of 15, 30, 60 min, 2, 6, 12, or 24 h. The maternal and cord plasma ACTH levels were higher than the levels in healthy nonpregnant women. There are no differences between the mean maternal (226 +/- 146 pg/ml) and cord (226 +/- 147 pg/ml) values of ACTH. The high ACTH levels of cord plasma remain unchanged for 30 min, decrease significantly during the 1-6 h after birth, because of the elimination process of the circulated foetal ACTH, and increase over the next 12-24 h and slightly thereafter indicating an initiation of neonatal pituitary ACTH secretion. The plasma ACTH level in the mothers with membranes ruptured for 1-5 h was significantly (P less than 0.05) higher compared with that in the mothers with membranes ruptured for less than 1 h. However, the duration of ruptured membranes appeared to have no effect on the cord blood ACTH level.