Longitudinal measurements of 17α-hydroxyprogesterone in premature infants during the first three months of life

Aims - To determine normal concentrations of 17α-hydroxyprogesterone (17OHP) for premature infants. Methods - 170HP was measured in 66 consecutive premature infants once a week during the first month, and once every two weeks thereafter, until the age of 3 months. The 17OHP values in 100 full term healthy neonates on the third day of life served as controls. Blood was sampled on filter paper using a neonatal radioimmunoassay kit. Findings were correlated with gestational age, birthweight, mode of delivery, Apgar scores, presence of respiratory distress syndrome and intake of maternal steroids. Results - Mean 17OHP was raised at 7 days of age (138.9, 46.3, 53.3, 29.9 nmol/l, respectively, for infants whose gestational age was under 29 weeks, 29 to 30 weeks, 31 to 32 weeks, and 33 weeks and above). It fell sharply in the first two weeks after which it gradually decreased further, reaching 32.7, 23.6, 16.9, and 13.0 nmol/l, respectively, by the age of 90 days. The mean (SEM) 17OHP concentration in full term infants on day 3 of life was 17.8 (8.9) nmol/l. These values were independent of the presence and severity of respiratory distress syndrome and of prenatal maternal steroids. Conclusions - The increased 17OHP concentrations found at birth fell to those found in term infants during the first three months of life in infants over 31 weeks of gestation. Postconceptional age is the most important factor determining 17OHP concentration.