[Seasonal differences in neonatal jaundice]

It is important to consider additional factors known to affect serum bilirubin levels in the newborn and that might yield new criteria for the diagnosis of physiological and non-physiological (or pathological) jaundice. The aim of this study was to analyze the seasonal differences of pathologic hyperbilirubinemia during the neonatal period.

One hundred and sixty-one consecutive newborn infants with pathologic hyperbilirubinemia who were admitted to our Neonatal Care Unit during three years were studied prospectively. Jaundice (and hyperbilirubinemia) was considered pathological if the time of appearance, duration or pattern of serially determined serum bilirubin concentrations varied significantly from that of physiological jaundice. Complete obstetric histories were obtained and examinations were performed at the time of admission. Seasonal differences in this population were studied.

We found more pathologic hyperbilirubinemia during the fall and less in winter, but these differences between seasons were not statistically significant. The only statistically significant differences were found in summer: more breastmilk jaundice (p < 0.05), more infants with maximum serum bilirubin > 20 mg/dl (p < 0.05) and more admissions from external delivery rooms (p < 0.05). We have not documented an association between weight loss of the newborn and the level of hyperbilirubinemia.

The higher temperature during the summer could contribute to the qualitative and quantitative differences found in this season, with a greater influence of breastfeeding and more severe hyperbilirubinemia. In general investigation of the cause of hyperbilirubinemia in healthy breastfed newborn infants is not indicated unless the serum bilirubin level exceeds 15 mg/dl, but this value could be higher in the summer.