Cortisol in amniotic fluid and cord blood in relation to prenatal betamethasone load and delivery.

The influence of maternal corticosteroid administration on the cortisol concentration in fetal blood and amniotic fluid (AF) was studied in women receiving betamethasone for prevention of IRDS. Thirty-four pregnant women in danger of spontaneous or induced preterm delivery were treated with 12 mg. of betamethasone daily for 3 days. AF was obtained by amniocentesis on the day before and the day following the betamethasone treatment and by amniotomy at delivery; cord arterial and venous blood was taken at delivery. Corresponding samples were obtained from 17 pregnant control subjects. All samples were analyzed in duplicate for cortisol by radioimmunoassay. The basal AF cortisol level rose with gestational age. The AF cortisol concentration fell from the basal value of 24.5 +/- 1.8 to 5.4 +/- 0.4 ng. per milliliter 3 days after the start of treatment, and it remained low at delivery if the treatment-delivery time was less than 1 week. An almost significant positive correlation (r = 0.543) was found between the cortisol concentration in cord arterial blood and AF. The cortisol concentration in cord blood in the controls was 108.2 +/- 14.3 ng. per milliliter in the arteries and 106.4 +/- 18.6 ng. per milliliter in the vein. Also, the cord blood cortisol level was depressed in betamethasone had been given within one week before delivery. The multifactorial influence on cord blood cortisol level prevents interpretation of the results as support for the concept that the human fetal adrenal is involved in labor initiation. The duration of gestation was not altered by the betamethasone treatment. The analysis of cortisol in the easily accessible amniotic fluid is suggested for estimating the function of the fetal adrenal cortex.