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The influence of gestational age on bilirubin conjugation in newborns
Author(s) -
ULLRICH D.,
FEVERY J.,
SIEG A.,
TISCHLER T.,
BIRCHER J.
Publication year - 1991
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1111/j.1365-2362.1991.tb01363.x
Subject(s) - gestational age , bilirubin , medicine , obstetrics , physiology , pregnancy , endocrinology , biology , genetics
. Unconjugated, mono‐ and diconjugated bilirubin levels were determined in serum soon after birth, and followed up for several days. Fourteen preterm neonates were studied with a gestational age below 33 weeks ( n = 7) or between 34 and 37 weeks ( n = 7), respectively, as well as 19 full‐term newborns either untreated ( n = 9) or treated by phototherapy ( n = 10). Bilirubin and its derivatives were analysed by alkaline methanolysis and spectrometry after separation by thin‐layer chromatography. In normal full‐term neonates total and unconjugated bilirubin reached peak levels at days 2–4. Thereafter, a decline of 11 % per day was detectable. Monoconjugates in serum amounted to 3.1 ± 1.1% of total pigment and remained at that level. The relative amount of diconjugates increased from 0.55 ± 0.25% (2–4th postnatal day) to 1.62 ± 0.99% (9–13th day of life). The rapid decline of unconjugated bilirubin paralleled by an increase of diconjugates are an expression of the maturation process for bilirubin conjugation. The premature neonates with less than 33 weeks gestation exhibited an increase of unconjugated serum bilirubin up to the 4–5th postnatal day, the decline thereafter amounted 2% per day. The fraction of 2.3 ± 1.1% monoconjugates was small and exhibited only a moderate increase in the follow up. In contrast diconjugates were undetectable or very low and remained at this level. These results suggest the presence of a more severe immaturity as well as a slower maturation process of bilirubin conjugation in preterm newborns. A subgroup of full‐term neonates treated by phototherapy showed highest serum bilirubin levels at the first days of life and the lowest monoconjugate fraction (1.2 ± 1±1%). In the follow up the monoconjugates rose slightly, whereas the diconjugate fraction remained very low. These findings in this subgroup of full‐term newborns might indicate a more severe conjugation defect for bilirubin as well as a bilirubin overload in respect to a limited bilirubin glucuronidation capacity. Analysis of bilirubin pattern in serum seems to allow prediction of the severity and the maturation rate of bilirubin conjugation.