6 beta-Hydroxycortisol levels in maternal urine of pregnancies complicated by prematurity.

Maternal urinary 6 beta-hydroxycortisol (6 beta-OHF) and creatinine levels were measured in 28 patients with singleton pregnancies admitted in apparent premature labor and in 17 women with singleton pregnancies delivered at term. Urine specimens were collected immediately after admission but prior to the initiation of active clinical intervention and management. Fourteen patients in true premature labor who were spontaneously delivered less than 24 hours after admission had significantly elevated 6 beta-OHF levels (1,144 +/- 210 ng/ml) compared to levels in 14 patients in false premature labor who were delivered more than 48 hours after admission (544 +/- 88 ng/ml). The mean ratio of 6 beta-OHF to creatinine was also elevated in patients in true premature labor (184.5) compared to ratios in patients delivered more than 48 hours after admission and in women in labor at or near term (range 123.4 to 128.6). The absolute levels of creatinine in all groups did not differ significantly, suggesting that the excretion of 6 beta-OHF proceeds independently of any change in renal function. Only in patients in the true premature labor group were 6 beta-OHF levels correlated with creatinine levels. However, in urine obtained within 24 hours prior to premature delivery, 6 beta-OHF levels did not appear to be related to the presence or absence of neonatal respiratory distress syndrome. It is concluded that measurement of 6 beta-OHF may provide an objective criterion for directing tocolytic therapy to those patients in true premature labor.