The relationship of prolactin in cord blood, gestational age and respiratory compliance after birth in newborn infants.

In 29 healthy newborns (gestational age 30-41 weeks) and 7 newborns with respiratory distress syndrome (gestational age 28-31 weeks) the prolactin levels in the cord blood and respiratory compliance was measured. Prolactin was determined by radioimmunoassay, the respiratory compliance was measured with the airway occlusion technique in spontaneously breathing newborns and with injection of known volumes and measuring the airway pressure in newborns with ventilatory support. In healthy newborns prolactin and gestational age were significantly correlated (r = 0.62, p less than 0.001), while prolactin did not correlate with respiratory compliance (r = 0.22, n. s.). Comparing 5 healthy newborns and the 7 RDS infants with prolactin values below 170 ng/ml, there was no significant difference in the prolactin levels, but in the compliance values. We conclude that prolactin does not directly influence lung maturation, but is associated with gestational age.