Corticotrophin releasing hormone levels in human plasma and amniotic fluid during gestation.

OBJECTIVE

Corticotrophin releasing hormone, a hypothalamic neuropeptide also made in placenta, may regulate fetal maturation in a stress-responsive manner. The objectives of this study were: (1) to determine if levels of corticotrophin releasing hormone in the amniotic fluid correlate with fetal lung maturation; (2) to confirm that third trimester plasma levels of corticotrophin releasing hormone are increased in patients with pregnancy-induced hypertension compared to normotensives, and (3) to increase the recovery of extracted corticotrophin releasing hormone from plasma and amniotic fluid.

DESIGN

(1) Levels of corticotrophin releasing hormone in amniotic fluid during the third trimester were compared with those of saturated phosphatidyl choline. (2) Corticotrophin releasing hormone levels were measured in a group of normotensive pregnant women during the entire gestation period. Corticotrophin releasing hormone levels during the third trimester were compared in normotensives and patients with pregnancy-induced hypertension.

PATIENTS

Twenty-one non-pregnant normal volunteers and 63 pregnant women.

MEASUREMENTS

Blood pressure, corticotrophin releasing hormone in plasma and amniotic fluid, and saturated phosphatidyl choline in amniotic fluid.

RESULTS

Corticotrophin releasing hormone levels in amniotic fluid samples during the third trimester ranged from 12 to 98 pmol/l and positively correlated with the saturated phosphatidyl choline levels, but not with gestational age. A significant difference existed in plasma corticotrophin releasing hormone concentration between gestational age-matched third trimester normotensive and hypertensive gravids: corticotrophin releasing hormone levels were significantly lower in normotensives (223 +/- 65 pmol/l) than in patients with pregnancy-induced hypertension (544 +/- 106 pmol/l, P = 0.001). Plasma corticotrophin releasing hormone increased with gestational age from 51 pmol/l (range 8.4-85) at 25-32 weeks to 375 pmol/l (range 35-1386) at 33-40 weeks. During the third trimester the rise in plasma corticotrophin releasing hormone conformed to an exponential mathematical model of a positive feedback loop between placental corticotrophin releasing hormone and fetal adrenal cortisol.

CONCLUSIONS

During the third trimester of pregnancy there is a positive correlation between the level of amniotic fluid corticotrophin releasing hormone and that of saturated phosphatidyl choline. The positive correlation between amniotic fluid corticotrophin releasing hormone and saturated phosphatidyl choline, but not between amniotic fluid corticotrophin releasing hormone and gestational age, suggests that a factor(s), such as stress, may affect both amniotic fluid corticotrophin releasing hormone and saturated phosphatidyl choline in parallel. Furthermore, our data are consistent with the hypothesis that the rise in placental corticotrophin releasing hormone is coupled to an increase in fetal glucocorticoid and lung maturation, and that stresses such as pregnancy-induced hypertension may accelerate this process.