Neonatal Hyperbilirubinemia: Study Identifies Risk Profile

Susan London

November 09, 2015

A set of maternal and obstetric risk factors readily available at birth predicts a greater than 100-fold variation in the incidence of nonhemolytic neonatal hyperbilirubinemia, according to a large population-based study published online November 9 in Pediatrics.

The analysis of more than a million singleton infants born in Sweden found that risk ranged from 0.2% for those having the most favorable combination of factors to 26% for those having the least favorable combination, report Mikael Norman, MD, PhD, from the Division of Pediatrics, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, and the Department of Neonatal Medicine, Karolinska University Hospital, both in Stockholm, Sweden, and colleagues.

The authors include in the article a colored scoring sheet for estimating an individual infant's risk.

"The risk factors identified and quantified herein enable simple and individualized risk prediction immediately after birth. Such assessment may be a good starting point for parental counseling and for professional decision-making on additional management in the neonatal period, targeting early detection of severe hyperbilirubinemia and thereby effective prevention of kernicterus," they write.

In an interview with Medscape Medical News, Vinod K. Bhutani, MD, a professor of pediatrics (neonatology) at the Lucile Salter Packard Children's Hospital, Stanford School of Medicine, Palo Alto, California, commended the research, describing it as "a major contribution."

The findings give rise to two key questions, he said: Can this profile be further refined to give an even more accurate prediction of risk, and can the identified risk factors be modified to improve outcomes, both for the current pregnancy and future pregnancies? "Each of those risk factors are obviously things that can be controlled [or] cannot be controlled. But they allow for both prenatal as well as postnatal practice pattern changes," he elaborated.

When asked whether the new risk profile will be applicable to infants born in the United States, Dr Bhutani said he definitely thinks it will. He noted that some of the included factors have been at least hinted at in smaller US studies. "What the Swedes have that the Americans do not have is such large national databases," which enable confirmation and better validation.

"I think we will see an echo of these findings probably from our Canadian colleagues, who have access to similar databases," he predicted. Also, it may be possible to validate the profile in the California Perinatal Quality Care Collaborative, which captures data on more than 90% of neonates admitted for intensive care in the state. "California is quite representative of the diversity that is seen in the US," he noted.

In the study, the investigators analyzed data on 1,261,948 singleton infants captured in the Swedish Medical Birth Register between 1999 and 2012. Overall, 1.9% of the infants had a diagnostic code for nonhemolytic hyperbilirubinemia, which in Sweden requires admission for neonatal care at any time up to a postnatal age of 28 days plus active treatment with phototherapy or exchange transfusion to reduce serum bilirubin.

Analyses identified a set of positive and negative risk factors having a medium or large effect size, defined as an adjusted odds ratio for neonatal hyperbilirubinemia of 1.5 or greater, or 0.5 or less. These factors were gestational age of 37 to 38 weeks (adjusted odds ratio [aOR], 2.83), failed vacuum extraction (aOR, 2.79), vacuum extraction (aOR, 2.22), Asian mother (aOR, 2.09), primiparous mother (aOR, 2.06), large-for-gestational-age infant (aOR, 1.84), obese mother (aOR, 1.83), and small-for-gestational-age infant (aOR, 1.66), as well as planned cesarean delivery (aOR, 0.45).

"The risk factors for development of severe hyperbilirubinemia identified herein add new knowledge to current standards," the investigators maintain. They recommend that existing models for hyperbilirubinemia risk prediction be revised to include as major risk factors a gestational age of 38 weeks, maternal obesity, primiparity, and infants large or small for gestational age, and to exclude maternal age of 25 years or older.

"An individualized score sheet available at birth, as suggested herein, may take hyperbilirubinemia risk assessment several steps forward in terms of accuracy of risk prediction," the investigators add. "Such an individualized risk prediction can be useful for parental counseling, planning of optimal timing for hospital discharge and follow-up visits, and timing of bilirubin determinations, before and after hospital discharge."

The authors and Dr Bhutani have disclosed no relevant financial relationships.

Pediatrics. Published online November 9, 2015.

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