Serum cortisol levels in very low birth weight infants of substance-abusing mothers

Recently, hypoadrenalism was described in extremely low birth weight infants. We have been measuring serum cortisol levels in very low birth weight (VLBW) infants to assess their adrenal function. It was noticed that infants of substance-abusing mothers (ISAM) had unusually high serum cortisol levels. To our knowledge, there are no data regarding serum cortisol levels in VLBW ISAM. The objective of our study was to determine if serum cortisol levels of VLBW ISAM are different from serum cortisol levels in VLBW infants without a history of maternal substance abuse. We reviewed medical records of infants with birth weight between 400 and 1300 gm who were born between July 1994 and June 1995. Seven ISAM who had serum cortisol levels drawn before 48 hours of life were identified. Seven infants matched for gestational age, antenatal steroid exposure, and birth weight served as control infants. Clinical characteristics, serum cortisol levels, and clinical outcome were compared between the two groups. Serum cortisol levels of all infants were measured by radioimmunoassay. The mean birth weight of the ISAM group was 834 gm (range 480 to 1175 gm), and the mean gestational age was 27.4 weeks. The mean birth weight of the control group was 921 gm (range 525 to 1230 gm) with a mean gestational age of 27.8 weeks. The mean serum cortisol level of the ISAM group was 65.3 micrograms/dl (range 11.9 to 144 micrograms/dl); it was significantly higher than that of the control group (mean cortisol level of 20.5 micrograms/dl; range 4.9 to 62.7 micrograms/dl) (p = 0.01, two-tailed). Our data suggest that maternal substance abuse significantly increases serum cortisol levels in VLBW infants. Studies in larger scale are needed to confirm our findings and to correlate cortisol levels in this group of patients with clinical outcome.