Cord bilirubin as a predictor for development of hyperbilirubinemia in term neonates

Introduction: Hyperbilirubinemia is a common problem among term newborns. Cord bilirubin level has been found to correlate well with day 3 bilirubin level. We studied whether cord bilirubin could predict risk of development of significant hyperbilirubinemia among term neonates. Methodology: Prospective study from October 2009 -July 2010. All newborns between 37 weeks -42weeks, birth weight > 2500 gram, Apgar score > 7 at 1 st & 5 th minute of life were included in the study. Cord blood, day 3 & day 5 bilirubin was collected. Maternal data & bilirubin values were collected & analyzed using SPSS software. Results: About 115 babies were studied. There was no significant difference in cord bilirubin & day 3 bilirubin between babies born to mothers < 30 years &> 30 years. There was no significant difference in bilirubin values bassed on mode of delivery. About 29.6% babies developed clinical jaundice & received phototherapy. Cord bilirubin levels had significant association with need of phototherapy. Cord bilirubin >/= 2.1 mg/dl predicted need for phototherapy with PPV of 90.3%. Maternal age, sex of baby, birth weight & gestational age had no significant effect on cord bilirubin levels. Cord bilirubin >/= 2.1 mg/dl predicted day 3 serum bilirubin > 15 mg/dl with sensitivity of 88 % & PPV of 77.49 %. The likelihood ratio with cord bilirubin > 2.1 mg/dl & day 3 serum bilirubin > 15 mg/dl was 9.316. Conclusion: Cord bilirubin is predictive of need of phototherapy & correlated well with day 3 bilirubin levels which would facilitate early management of neonatal hyperbilirubinemia.


Introduction
The commonest problem encountered during neonatal period among term neonates is Hyperbilirubinemia [1], which prolongs hospital stay in a majority of babies. Hyperbilirubinemia is defined as a serum total bilirubin concentration greater than 95th centile for hour of life.  [2,3,4]. Of late, Cord bilirubinlevel is being increasingly studied to define a subgroup of newborns that are at higher risk for developing significant hyperbilirubinemia. Hence this study was done to assess cord bilirubin as a predictor of neonatal hyperbilirubinemia.
Objective: To determine whether cord bilirubin level could predict risk of development of significant hyperbilirubinemia among term neonates. Exclusion criteria: Babies who were of preterm or post term gestation, birth weight < 2500 gram, Apgar score less than 7 at 5 minutes, Babies with major congenital malformations were excluded from the study.

Methodology
Parental consent was obtained. Under aseptic conditions umbilical cord blood of the newborn was collected at the time of delivery & serum bilirubin level was estimated by Jendrassik method in the biochemistry department on all days. All newborns were examined for clinical jaundice by the investigator & a paediatric consultant. If found icteric treatment was started according to protocol. On day 3 & day 5, serum bilirubin level was estimated.
Interventions: Phototherapy to icteric babies as per standard unit protocol.
Data Analysis: Data collected were enrolled in excel sheets & was analyzed using SPSS 17 version (Statistical Package for Social Science). A p-value of <0.05 was considered significant.
There is an association between bilirubin levels in cord blood & later neonatal bilirubin concentration [6,7,8]. Mean bilirubin levels in cord blood range from 1.4 to 1.9 mg/dl [9,10] & elevated cord bilirubin levels was associated with an increased risk of hyperbilirubinemia [7,9,10]. Risenberg et al [11] observed that babies with cord bilirubin more than 4mg/100ml were at risk of developing severe hyperbilirubinemia. Rosenfeld et al., [12] concluded that babies with cord bilirubin level < 2mg/dl had 4% chance of developing significant jaundice as compared to a 25% chance of developing significant jaundice in newborns with level > 2mg/dl. Knudson A [6] noted that need of phototherapy was statistically significant among newborns with cord bilirubin levels > 2.3 mg/dl as compared to babies with bilirubin < 2.3 mg/dl. Mathias Katfer et al., [13] observed that newborns with cord bilirubin > 30 micromol/ litre predicted need of phototherapy with a sensitivity of 90 % & a negative predictive value of 99.1 %. Serum cord total bilirubin levels can define a subgroup of infants who are at a higher risk for developing significant hyperbilirubinemia& requirement of phototherapy. Yamauchi Y et al., [7] observed that babies delivered by caesarean section had significant lower values of cord bilirubin as compared to babies delivered vaginally which was explained due to decreased placental transfusion during caesarean section. In our study there was no significant difference based on the mode of delivery. Srivastsav N et al., [14] in his study comparing newborns born to mothers with age < 30 years and mothers > 30 years found that babies born to younger mothers had higher bilirubin on day 3 & day 5. However no statistically significant difference was observed on cord bilirubin. In our study there was no statistically significant difference in the cord bilirubin level & day 5 bilirubin in babies born to mothers < 30 years of age as compared to mothers >30 years of age.

Conclusion
Umbilical cord bilirubin is useful in predicting the postnatal bilirubin value on day 3 & need for phototherapy in normal term newborns. Cord bilirubin cut off of > / = 2.1 mg/dl among term neonates is a good predictor of total serum bilirubin > 15 mg/dl with good sensitivity & positive predictive value which would facilitate targeted intervention of babies at high risk of hyperbilirubinaemia in a safe & cost effective manner.

Recommendations:
Umbilical cord blood bilirubin of term newborn babies would facilitate early intervention in the management of neonatalhyperbilirubinemia thereby reducing hospital stay in a resource limited country like ours.

Abbreviations:
CB-cord bilirubin TSB-total serum bilirubin PPV-positive predictive value LR-likelihood ratio PT-phototherapy Funding: Nil, Conflict of interest: Nil Permission from IRB: Yes