Developmental pattern of urinary epidermal growth factor in the premature infant and the influence of gender.

We report the cross-sectional pattern of first day urinary epidermal growth factor/creatinine (EGF/Cr) levels in 159 appropriate for gestational age infants born at 26-41 weeks gestation. EGF/Cr levels rose significantly earlier in female infants than levels in male infants. In female infants levels were similar to term levels beginning at 30-32 weeks. Mean EGF/Cr levels in male infants were similar to term values beginning at 32-34 weeks. We could not demonstrate any influence from acute perinatal events on EGF/Cr levels. In a subset of 28 infants, a weekly longitudinal study of urinary EGF/Cr levels was undertaken. The urinary EGF/Cr pattern correlated significantly with both corrected gestational and postnatal ages. A significant change in the EGF/Cr pattern was observed at a corrected gestational age of 32 weeks and at 4 weeks postnatal age. There was no significant difference in EGF/Cr levels between males and females. Our results demonstrated a significant difference in first day urinary EGF/Cr levels between female and male preterm infants during the early third trimester. This difference was seen at a time in gestation when other gender-specific maturational and growth differences are noted. When infants born at less than 32 weeks gestational age were followed longitudinally, the urinary EGF/Cr pattern, when expressed by corrected gestational age, was significantly modified from that in the cross-sectional study.