Introduction: Newborn jaundice is caused by increased levels of bilirubin in the blood of the newborn during the first days after birth. Generally, neonatal jaundice does not need to be treated, however, if the blood bilirubin concentration becomes too high, it can cause neurological damage. Due to the prevalence of neonatal jaundice, it is important to assess its risk factors and their importance. This study at the National University Hospital of Iceland from 1997-2018, determines the risk factors for severe neonatal jaundice and their significance.

Material and methods: This was a retrospective case control study conducted at the National University Hospital of Iceland. It included all newborns diagnosed with severe jaundice (≥350 micromol/L) following a pregnancy of at least 37 weeks that were treated at the National University Hospital of Iceland from 1997 until 2018. General information on the pregnancy, health of the child at birth, as well as the diagnosis and treatment of jaundice was collected. 339 children met the inclusion criteria for this study. For each child diagnosed with severe jaundice one control was found.

Results: The incidence of severe jaundice from 1997 to 2018 was 0.52%. Of the 339 children, 16% were found to have a known significant risk factor for severe neonatal jaundice. The most common were ABO incompatibility and cephalohematoma. Only one child had severe neonatal jaundice because of Rhesus incompatibility. Regression analysis revealed the significant risk factors as followins: shorter pregnancy, bruising at birth, male gender, discharge before 36 hours after birth and relative weight loss the first five days of life. 33% were diagnosed during a ­routine doctor's examination five days after birth.

Conclusion: Early discharge from the hospital and ­relative weight loss the first few days after birth are significant independent risk factors for severe neonatal jaundice. Most cases were diagnosed during a routine doctors five-day check- up. This indicates that there is room for improvement in the evaluation of jaundice in post-natal home care. Monitoring of neonates with Rhesus incompatibility in Iceland exemplary. Boys are at an increased risk for severe neonatal jaundice. It is espe­cially noteworthy given that the negative effect of jaundice on learning ability appears to be greater in boys than in girls.

Table I  Significant risk factors for severe neonatal jaundice at the National University Hospital of Iceland from 1997-2018 according to multiple factor analysis.

Table II   Comparison of potential risk factors for severe neonatal jaundice at the National University Hospital of Iceland from 1997-2018 and the outcome of single-factor analysis.

Figure I   Bar graph showing the incidence of severe neonatal jaundice in full-term neonates at National University Hospital of Iceland 1997-2018, calculated from all full-term neonates born at the National University Hospital of Iceland each year.

Figure II   A bar chart showing a comparison of the proportion of cases and criteria by pregnancy length in full-term neonates at National University Hospital of Iceland, 1997-2018.

Figure III Bar chart showing the age at which the cases were diagnosed.

Figure IV   Box chart showing the distripution af serum bilirubin measurements for cases.