Neonatal jaundice in full-term infants. Role of breast-feeding and other causes

What Happens in the Gut during the Formation of Neonatal Jaundice-Underhand Manipulation of Gut Microbiota?

Jaundice is a symptom of high blood bilirubin levels affecting about 80% of neonates. In neonates fed with breast milk, jaundice is particularly prevalent and severe, which is likely multifactorial. With the development of genomics and metagenomics, a deeper understanding of the neonatal gut microbiota has been achieved. We find there are accumulating evidence to indicate the importance of the gut microbiota in the mechanism of jaundice. In this paper, we present new comprehensive insight into the relationship between the microbiota and jaundice. In the new perspective, the gut is a crucial crossroad of bilirubin excretion, and bacteria colonizing the gut could play different roles in the excretion of bilirubin, including Escherichia coli as the main traffic jam causers, some Clostridium and Bacteroides strains as the traffic police, and most probiotic Bifidobacterium and Lactobacillus strains as bystanders with no effect or only a secondary indirect effect on the metabolism of bilirubin. This insight could explain why breast milk jaundice causes a longer duration of blood bilirubin and why most probiotics have limited effects on neonatal jaundice. With the encouragement of breastmilk feeding, our perspective could guide the development of new therapy methods to prevent this side effect of breastfeeding.

Baby-Friendly Hospital Initiative Is Associated with Lower Rates of Neonatal Hyperbilirubinemia

Background: The Baby-Friendly Hospital Initiative (BFHI) advances practices that support exclusive breastfeeding. BFHI practices are associated with increased breastfeeding rates, however, other patient outcomes are not well described. This study examined the association of BFHI practices with hyperbilirubinemia and phototherapy between groups of newborns born before and after BFHI implementation at an urban, tertiary academic medical center in South Carolina. Materials and Methods: We conducted a retrospective study of healthy, term newborns born between July and September 2011 (n = 956), before BFHI implementation, and newborns born during the same period in 2013 (n = 1,131) after BFHI implementation. Primary outcomes were neonatal hyperbilirubinemia, phototherapy treatment, and hospital readmissions for hyperbilirubinemia within 30 days of discharge. We compared rates of outcomes between the study groups using unadjusted and adjusted odds ratios (OR). Results: Among newborns born before versus after BFHI implementation, 20.3% versus 6.98% were diagnosed with hyperbilirubinemia (p < 0.001), 5.75% versus 1.95% received phototherapy (p < 0.001), and 0.31% versus 0.35% were readmitted to the hospital for hyperbilirubinemia within 30 days (p = 0.88). In adjusted analyses, newborns born after BFHI implementation were significantly less likely to develop neonatal hyperbilirubinemia (OR 0.28 [95% confidence intervals; CI 0.20-0.37]) and receive phototherapy treatment (OR 0.27 [95% CI 0.15-0.49]) than newborns born before BFHI implementation. Conclusions: Implementation of BFHI practices is associated with significant decreases in neonatal hyperbilirubinemia and phototherapy without affecting readmission rates. Exclusive breastfeeding has traditionally been considered a risk factor for the development of neonatal jaundice. This study demonstrates that BFHI practices may mitigate that risk.

Association between rooming-in policy and neonatal hyperbilirubinemia

BACKGROUND

The practices promoted by the Baby-friendly Hospital Initiative have become a part of current mainstream postpartum infant care. Rooming-in to facilitate skin-to-skin contact and breastfeeding is a major component of this initiative. However, whether rooming-in is associated with admission for neonatal hyperbilirubinemia has seldom been reported. The aim of this study was to evaluate the association between rooming-in and neonatal hyperbilirubinemia.

METHODS

This was a retrospective cohort study. Term neonates were consecutively enrolled from the nursery of a medical center from January 2011 to December 2013. During the study period, rooming-in care was strongly encouraged according to the World Health Organization guidelines, if the parents agreed. The endpoint was defined as admission for phototherapy. Risk of neonatal hyperbilirubinemia in rooming-in neonates was calculated. Potential confounding factors, including exclusive breastfeeding, potential ABO incompatibility, Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency, and body weight loss (BWL), were adjusted by multiple logistic regression models.

RESULTS

Totally, 3341 infants were enrolled in this study after excluding 40 infants admitted for other reasons. The rooming-in rate increased yearly during the study period. However, the rate of neonatal hyperbilirubinemia also increased simultaneously. The odds ratio (OR) of neonatal hyperbilirubinemia in the rooming-in group was 7.04 (95% CI, 4.41∼11.24). The rooming-in group demonstrated a higher percentage of exclusive breastfeeding and BWL >10% at 3 days of age. After adjusting for potential confounding factors, rooming-in was still a significant risk factor for neonatal hyperbilirubinemia (OR: 8.48; 95% CI: 5.04∼14.25).

CONCLUSIONS

The practice of rooming-in is now part of the mainstream postpartum newborn care. However, the increased incidence of neonatal hyperbilirubinemia is a potential side effect of which healthcare providers should be aware. Further research is needed to confirm the role of rooming-in in neonatal hyperbilirubinemia.

Preventable newborn readmissions since passage of the Newborns' and Mothers' Health Protection Act

BACKGROUND

Congress passed the Newborns' and Mothers' Health Protection Act in 1996, reversing the trend of shorter newborn nursery lengths of stay. Hope existed that morbidities would lessen for this vulnerable population, but some reports indicate that the timeliness and quality of postdischarge care may have worsened in recent years.

OBJECTIVE

Our goal was to determine risk factors for the potentially preventable readmissions because of jaundice, dehydration, or feeding difficulties in the first 10 days of life in Pennsylvania since passage of the Newborns' and Mothers' Health Protection Act.

PATIENTS AND METHODS

Birth records from 407,826 newborns > or = 35 weeks' gestation from 1998 to 2002 were merged with clinical discharge records. A total of 2540 newborns rehospitalized for jaundice, dehydration, or feeding difficulties in the first 10 days of life were then compared with 5080 control infants. Predictors of readmission were identified by using multiple logistic regression analysis.

RESULTS

An unadjusted comparison of baseline characteristics revealed numerous predictors of readmission. Subsequent adjusted analysis revealed that Asian mothers, those 30 years of age or older, nonsmokers, and first-time mothers were more likely to have a readmitted newborn, as were those with diabetes and pregnancy-induced hypertension. For neonates, female gender and delivery via cesarean section were protective for readmission, whereas vacuum-assisted delivery, gestational age < 37 weeks, and nursery length of stay < 72 hours were predictors of readmission in the first 10 days of life.

CONCLUSIONS

Although readmissions for jaundice, dehydration, and feeding difficulties may be less common for some minority groups and Medicaid recipients in the era of the Newborns' and Mothers' Health Protection Act compared with nonminorities or privately insured patients, several predictors of newborn readmission have established associations with inexperienced parenting and/or breastfeeding difficulty. This is one indication that this well-intentioned legislation and current practice may not be sufficiently protecting the health of newborns and suggests that additional support for mothers and newborns during the vulnerable postdelivery period may be indicated.

Evaluation of a new transcutaneous bilirubinometer in Chinese newborns

OBJECTIVE

To evaluate the use of a new transcutaneous bilirubinometer (JM-103 Minolta Airshields) for detection of hyperbilirubinaemia in term or near-term healthy Chinese newborns.

METHODS

Transcutaneous bilirubin (TcB) was used to screen for severe hyperbilirubinaemia in newborn infants. Blood was taken for total serum bilirubin (TSB) measurement if the initial TcB level was higher than the 40th centile in Bhutani's nomogram. Paired TcB and TSB results were then reviewed over 6 months. The correlation as well as the mean difference between the two methods were calculated. The clinical application of TcB with Bhutani's nomogram in the prediction of severe hyperbilirubinaemia in low-risk, medium-risk and high-risk thresholds for phototherapy was also analysed.

RESULTS

997 paired TcB and TSB measurements were evaluated in term or near-term newborns. TcB was significantly correlated with TSB, with a correlation coefficient of 0.83 (p<0.001). Their mean difference was 21.7 micromol/l (SD 21.2, p<0.001), with the 95% limits of agreement between -19.9 and 63.3 micromol/l. In both low-risk and medium-risk thresholds for phototherapy, using the 75th centile of Bhutani's nomogram as threshold, TcB could identify all cases and had a sensitivity and negative predictive value of 100% each, a specificity of 56% and positive predictive value of 23%. For high-risk cases, using the 75th centile as cut-off, the sensitivity and negative predictive value were reduced to 86.7% and 97.0%, respectively.

CONCLUSION

An accurate point-of-care bilirubin analyser facilitates bilirubin screening and avoids unnecessary blood tests. Although using the transcutaneous bilirubinometer JM-103 might result in a significant difference between TcB and TSB measured in Chinese newborns, combining the use of TcB and the 75th centile in Bhutani's nomogram as the cut-off level can identify all cases of significant hyperbilirubinaemia.

Genetic variation of human UDP-glucuronosyltransferase: implications in disease and drug glucuronidation

The uridine diphosphate (UDP)-glucuronosyltransferases (UGTs) are key enzymes in human detoxication of xeno- and endobiotics. Potentially toxic endogenous compounds such as bilirubin, or exogenous compounds such as drugs, pesticides, and carcinogens, are generally transformed into water-soluble glucuronides for excretion in bile and urine. The UGTs are encoded by a multigene family in humans. A relatively small number of human enzymes catalyze the glucuronidation of thousands of compounds. Genetic variations and single nucleotide polymorphisms (SNPs) within the UGT genes are remarkably common, and lead to genetic polymorphisms. The multiplicity of transferases, some exhibiting overlapping substrate specificity, may provide functional compensation for genetic deficit in some cases. Genetic variation may cause different phenotypes by affecting expression levels or activities of individual UGTs. This inter-individual variation in UGTs has resulted in functional deficit affecting endogenous metabolism and leading to jaundice and other diseases. Disruption of the normal metabolic physiology, by the reduction of bile acid excretion or steroid glucuronidation, may lead to cholestasis and organ dysfunction. Deficient glucuronidation of drugs and xenobiotics have an important pharmacological impact, which may lead to drug-induced adverse reactions, and even cancer. Additional novel polymorphisms in this gene family are yet to be revealed and studied, but will have a profound effect on the development of new drugs and therapies.

Neonatal hyperbilirubinemia and Gilbert's syndrome

The role of Gilbert's syndrome (GS) in neonatal hyperbilirubinemia, characterized by bilirubin levels higher than 223 microMol/L during the first seven days of life, has been investigated, evaluating the frequency of GS genotype (A(TA)7TAA polymorphism in the promoter of the gene encoding UGT1). The frequency of GS was significantly higher in the hyperbilirubinemic group, even though neither the peak of bilirubin, nor the day on which the highest value was found, differed according to genotype. The normalization of bilirubin levels was slower in neonates with GS. These results confirm the idea that GS is one of the factors contributing to neonatal hyperbilirubinemia, but that other factors play a role in determining neonatal jaundice. The slower decrease of bilirubin levels in A(TA)7TAA homozygous neonates confirms that GS is an important factor in determining a prolonged neonatal jaundice.

Is breastfeeding really favoring early neonatal jaundice?

OBJECTIVE

The purpose of this study was to evaluate the development of significant hyperbilirubinemia in a large unselected newborn population in a metropolitan area with particular attention to the relationship between type of feeding and incidence of neonatal jaundice in the first week of life.

STUDY DESIGN

A population of 2174 infants with gestational age >/=37 weeks was prospectively investigated during the first days of life. Total serum bilirubin determinations were performed on infants with jaundice. The following variables were studied: type of feeding, method of delivery, weight loss after birth in relationship to the type of feeding, and maternal and neonatal risk factors for jaundice. Statistical analyses were performed using the z test for parametric variables and the t test for nonparametric variables. In addition, the multiple logistic regression allows for the estimation of the role of the individual characteristics in the development of hyperbilirubinemia. Data concerning serum bilirubin peak distribution in jaundiced newborns were analyzed using a single and a double Gaussian best fit at least squares. The t test was performed to compare 2 values (high and low) of the serum bilirubin peak in breastfed and supplementary-fed infants with those in bottle-fed infants.

RESULTS

The maximal serum bilirubin concentration exceeded 12.9 mg/dL (221 micromol/L) in 112 infants (5.1%). The study demonstrated a statistically significant positive correlation between patients with a total serum bilirubin concentration >12.9 mg/dL (221 micromol/L) and supplementary feeding; oppositely, breastfed neonates did not present a higher frequency of significant hyperbilirubinemia in the first days of life. However, best Gaussian fitting of our data suggests that a small subpopulation of breastfed infants have a higher serum bilirubin peak than do bottle-fed infants. Newborns with significant hyperbilirubinemia underwent a greater weight loss after birth compared with the overall studied population, and infants given mixed feeding lost more weight than breastfed and formula-fed newborns, indicating that formula has been administered in neonates who had a weight loss beyond a predetermined percentage of birth weight. Significant hyperbilirubinemia was also strongly associated with delivery by vacuum extractor, some perinatal complications (cephalohematoma, positive Coombs' test, and blood group systems of A, AB, B, and O [ABO] incompatibility) and Asian origin. Multiple logistic regression analysis shows that supplementary feeding, weight loss percentage, ABO incompatibility, and vacuum extraction significantly increase the risk of jaundice, while only cesarean section decreases the risk.

CONCLUSION

The present study confirms the important role of fasting in the pathogenesis of neonatal hyperbilirubinemia, although breastfeeding per se does not seem related to the increased frequency of neonatal jaundice but to the higher bilirubin level in a very small subpopulation of infants with jaundice. In fact, in the breastfed infants, there is a small subpopulation with higher serum bilirubin levels. These infants, when starved and/or dehydrated, could probably be at high risk of bilirubin encephalopathy.

Molecular genetic basis of Gilbert's syndrome

Gilbert's syndrome, an hereditary, chronic, mild, unconjugated hyperbilirubinaemia resulting from impaired hepatic bilirubin clearance and otherwise normal liver function, is arguably the most common syndrome known in humans. Recent molecular genetic studies have determined that the clinical phenotype can be described by a dinucleotide polymorphism in the TATA box promoter of the bilirubin uridine diphosphate-glucuronosyltransferase (UGT-1A1) gene, most frequently (TA)7TAA, affecting up to 36% of Africans, but only 3% of Asians. However, a second common heterozygous mutation in the coding exon 1 of the UGT-1A1 gene (G71R) can also cause the Gilbert's phenotype in Japanese and Asians. The clinical phenotype may not be apparent as frequently as the determined genotype, due to environmental factors such as alcohol-induced hepatic bilirubin glucuronidation, reducing serum bilirubin levels and causing a latent condition. Gilbert's disease is a contributory factor of prolonged neonatal jaundice in breast-fed infants and may precipitate jaundice when coinherited with other disorders of haem metabolism. The genetic variation described as Gilbert's syndrome may lead to pharmacological variation in drug glucuronidation and unexpected toxicity from therapeutic agents.

Gilbert's syndrome is a contributory factor in prolonged unconjugated hyperbilirubinemia of the newborn

OBJECTIVE

Prolonged neonatal jaundice, beyond day 14 of life, is very common and of concern to the clinician. The aim of this study was to investigate whether a genetic mutation in the bilirubin UGT1A1 gene, which has been associated with Gilbert's syndrome in adults, is a contributory factor in prolonged neonatal jaundice.

STUDY DESIGN

Blood was collected from 85 term newborns with unexplained hyperbilirubinemia, and DNA was prepared. The neonates were divided into 6 groups depending on whether they were breast-fed or bottle-fed and whether they had acute, prolonged, or very prolonged jaundice. UGT1A1 TATA promoter genotyping (DNA test for Gilbert's syndrome) was performed on all samples, and analysis of the entire UGT1A1 coding sequence was performed in a representative sample (11 of 26) of very prolonged cases.

RESULTS

In addition to the known common UGT1A1 TATA alleles (TA6 and TA7), a novel TATA allele (TA5) in a neonate with very prolonged jaundice was identified. Statistical analysis of the TATA genotype distributions within the group of breast-fed neonates revealed significant differences among the acute, prolonged, and very prolonged subgroups (.05 > P >.01): the incidence of familial hyperbilirubinemia genotypes (7/7 and 5/7) is 5 times greater in very prolonged cases (31%) relative to acute cases (6%). Neonates with prolonged jaundice from family pedigrees were observed to demonstrate the Gilbert's phenotype as children or young adults.

CONCLUSIONS

A genetic predisposition to develop prolonged neonatal hyperbilirubinemia in breast-fed infants is associated with TATA box polymorphism of the UGT1A1 gene and will be recognized as Gilbert's syndrome in adulthood.

Early prediction of neonatal hyperbilirubinemia

The study aim was to predict, using serum bilirubin level measured 18 to 24 hours (SB, 18-24) after birth, the occurrence of peak serum bilirubin level > 15 mg/dL (hyperbilirubinemia) or the requirement of phototherapy, any time from the second to fifth postnatal day. The study was conducted on a prospective cohort of 274 neonates born in north India. The main outcome measures were (a) hyperbilirubinemia and (b) phototherapy. Serum bilirubin level was estimated at 18-24 hours of age and then daily from second to fifth postnatal day. Exclusion criteria were Rh incompatibility, asphyxia and life threatening congenital malformations; and neonates of women with gestational diabetes or history intake of drugs affecting the fetal liver. Hyperbilirubinemia was found in 12.8%; and 19.3% neonates received phototherapy. Dichotomous SB 18-24, using a cut-off of > 3.99 mg/dL, as the "prediction test" had the following sensitivity and specificity for predicting (a) hyperbilirubinemia: 67% and 67%, respectively, and (b) the treatment with phototherapy: 64% and 68%, respectively. We concluded that by using SB 18-24 as the "prediction test", approximately two-thirds of neonates were test negative and had about one in ten chances of re-admission for treatment of hyperbilirubinemia, if discharged. After further validation, our results will be of benefit to neonates delivered in developing countries.

Beta glucuronidase and hyperbilirubinaemia in breast fed infants of diabetic mothers

A prospective study was performed comparing bilirubin concentrations in 10 breast fed term infants of diabetic mothers (IDM) to those of 10 breast fed normal term infants. The beta-glucuronidase concentrations in serum and breast milk were assayed in the respective mothers. Significantly higher bilirubin concentrations were noted in the IDM group. Serum and breast milk beta-glucuronidase concentrations were significantly higher in diabetic mothers as compared with those of non-diabetic mothers. We suggest that the high concentration of beta-glucuronidase in breast milk of diabetic mothers is an additional important cause leading to hyperbilirubinaemia in their breast fed infants.

Assessment of hyperbilirubinemia in full-term infants: Part II

The nurse practitioner plays an important role in assessing infants for factors that may contribute to unconjugated bilirubinemia. Healthy, full-term infants with unconjugated hyperbilirubinemia and no evidence of hemolysis require monitoring of their total serum bilirubin levels and stooling patterns, and they need encouragement to feed more frequently to resolve the hyperbilirubinemia. Promoting frequent breast-feeding is essential, especially for infants with unconjugated hyperbilirubinemia. For those infants with evidence of hemolysis or exaggerated physiologic jaundice, more advanced medical intervention such as phototherapy and exchange transfusion are available when indicated.

The relationship between rooming-in/not rooming-in and breast-feeding variables

We studied the relationship between rooming-in/not rooming-in and breast-feeding variables such as breast feeding frequency, breast milk intake, supplements of other human milk or 5% glucose solution, cumulative weight loss, weight recovery and hyperbilirubinemia. We found that the breast feeding frequency was significantly higher in infants rooming-in than in those not rooming-in. Intake of breast milk on days 3 and 5 was significantly lower and maximum weight loss was significantly higher in infants rooming-in than in those not rooming-in. Infants rooming-in also had less supplement of other human milk compared with non-rooming-in infants (p less than 0.01). However, the weight increase per day from minimum to weight on day seven was higher in infants rooming-in than in non-rooming-in infants (39.3 +/- 21.4 g/day vs. 31.4 +/- 15.3 g/day, p less than 0.01). The frequent suckling by rooming-in infants may explain, in part, the better weight gain, since frequent suckling may decrease energy consumption by reducing movement and crying during the early days of life, thus contributing to better weight gain. Our study suggests that some of the neonatal feeding problems related to breast feeding could be eliminated by education of mothers and nurses and by changes in hospital policies and practices in breast feeding.

Breastfeeding and breast milk jaundice

Two Types of jaundice associated with breast-feeding are recognized. The first type is early onset breastfeeding jaundice which may result from caloric deprivation and/or insufficient frequency of feeding. This type of jaundice can be prevented or treated by encouraging mothers to nurse as frequently as possible, particularly if the bilirubin level is rising. The second type is later onset, prolonged jaundice, known as the breast milk jaundice syndrome which is associated with one or more abnormalities in the maternal milk itself. Breast milk jaundice syndrome generally needs no therapy if serum bilirubin concentrations remain below 270 mumol/l in healthy full-term infants. When the serum bilirubin concentration is above 270 mumol/l and rising, temporary interruption of breastfeeding may be indicated.

Difference in TcB readings between full term newborn infants born vaginally and by cesarean section

We studied the influence of method of delivery on TcB readings at the forehead and sternum in full term neonates in the first week of life. Our present study demonstrated that TcB readings at the forehead and sternum of the infants delivered by cesarean section were significantly lower than readings from infants delivered vaginally without complications, from day 1 to day 7 of life (p less than 0.05). This is probably due to the decreased placental transfusion at cesarean section. The present study suggests that the degree of placental transfusion or time of cord clamping may be more influential than meconium passage or weight loss on serum bilirubin levels in the first week of life.

Transcutaneous bilirubinometry in normal Japanese infants

We performed TcB readings in healthy full-term breast-fed Japanese infants from birth to seven days, and attempted to establish the normal range. TcB readings from Japanese infants were significantly higher over a longer period compared with Caucasian infants. The age of peak TcB readings in Japanese newborn infants was day 6, significantly later than that of Caucasian infants, day 3-4. We also attempted to estimate the total serum bilirubin concentrations using regression line relating TcB readings to serum bilirubin concentrations. Our study demonstrated that estimated total serum bilirubin concentration from forehead TcB readings was 0.56 +/- 0.35 mg/dl at birth, thereafter increasing to 6.8 +/- 0.5 mg/dl on day 1 and reaching a maximum of 12.6 +/- 2.5 mg/dl on day 6. These values and pattern in Japanese neonatal jaundice were significantly different from those of Caucasian children, but were similar to values and patterns from American Indians, Alaskan Eskimo, and other Asian full-term newborn infants. Thus TcB measurement may be useful for observation of the course of neonatal jaundice.

Breast milk jaundice in preterm infants

A retrospective study was performed comparing bilirubin levels in 40 preterm newborns with uncomplicated courses fed a combination of premature breast milk and formula to those of 60 comparable preterm newborns fed formula only. A significantly higher bilirubin level was noted in the group fed the combined diet on the 6th day of life and on the day of discharge. Seventy-six and seven tenths percent of the preterm infants fed breast milk and formula met the criteria for phototherapy, whereas only 45 percent were treated in the group fed formula alone. Our findings indicate that premature breast milk might cause early and late increase in bilirubin levels in healthy preterm newborns.

Neonatal jaundice and fatty acid composition of the maternal diet

The role of serum fatty acid composition in neonatal jaundice was studied by comparing the incidence of jaundice among 332 newborn infants receiving breast milk from mothers on a diet with either a low (0.1, n = 145) or a high (1.5, n = 187) polyunsaturated to saturated fatty acid (P/S) ratio. The diet was started immediately after delivery. The composition of fatty acids in the breast milk and sera of the mothers and in the sera of the newborns was evaluated from a random sample of 15 mother-newborn pairs on the control diet (low P/S ratio) and 19 pairs on the experimental diet. Five days after delivery the relative amounts of fatty acids, especially that of linoleate, in the sera of the mothers differed significantly depending on the diet. Differences were also observed in breast milk samples taken three, four or five days after delivery and in the sera of the newborns sampled at the age of four or five days. Nine of the 145 newborn infants (6.2%) in the control group had to be treated with light therapy compared with 12 out of 187 (6.4%) of the newborn infants in the experimental group (high P/S ratio). Serum bilirubin concentrations were 142.5 mumol/l (SD 65.8) and 140.7 mumol/l (SD 73.5) in the experimental and control groups, respectively, at the age of five days. It appears that the changes in the composition of serum fatty acids reached in this study had no effect on the neonatal jaundice.

Fecal bilirubin excretion and serum bilirubin concentrations in breast-fed and bottle-fed infants

To assess the rate of excretion of bilirubin in the stools and its effects on serum bilirubin concentrations, we studied 24 breast-fed and 13 bottle-fed infants during the first 3 days after birth. Bottle-fed infants passed significantly more stool (3-day totals, 82 vs 58 gm, P less than 0.001), excreted more bilirubin (3-day totals, 23.8 vs 15.7 mg, P less than 0.05), and had lower serum bilirubin values (day 3, 6.8 vs 9.5 mg/dl, P less than 0.02). Among the breast-fed infants, greater stool output was associated with greater fecal bilirubin excretion (r = 0.56, P less than 0.05) and lower serum bilirubin concentrations (r = 0.66, P less than 0.001). Our data suggest that hyperbilirubinemia in breast-fed infants may be related to a delay in bilirubin clearance resulting from low stool output.

Incidence of hyperbilirubinemia in breast- vs. formula-fed infants

A retrospective study of 233 consecutively born full-term infants was performed to determine the effect of several variables on the development of hyperbilirubinemia. Thirty-five (15%) of the infants developed peak bilirubin levels greater than 12 mg/dl in the first week of life. Step-wise multiple regression analysis revealed that breast-feeding was the most predictive of a group of eight variables for the development of hyperbilirubinemia greater than 12 mg/dl. The correlation between type of feeding and hyperbilirubinemia was significant (p less than 0.02). None of the other factors evaluated was significantly associated with hyperbilirubinemia. Breast-fed infants also were found to have a significantly higher incidence of hyperbilirubinemia greater than 15 mg/dl; 12 of 101 (12%) infants compared with 2 of 117 (2%) formula-fed infants (p less than 0.002). This group of infants accounted for the increased incidence of hyperbilirubinemia greater than 12 mg/dl in breast-fed infants. There was no significant correlation between weight loss and development of hyperbilirubinemia in the breast-fed infants.

Jaundice in full term healthy neonates--a population study

A geographically based population of 498 full term, appropriate for gestational age, healthy, singleton neonates was used to study the effect of obstetric and nursery practices on the occurrence of neonatal jaundice. At 3-4 days 56% of babies became visibly jaundiced (plasma bilirubin (PB) greater than 100 mumol/l) and 10% were hyperbilirubinaemic (PB greater than 200 mumol/l). Less mature babies, those slow to pass meconium and those who had lost weight at 4 and 7 days were more likely to be jaundiced. Obstetric practices, drugs given during labour, mother's or baby's blood group, natural illumination, plethora, extravasated blood or mode of feeding were found to have no effect. No benefit from giving supplementary milk or dextrose to breast fed babies was discovered. At 6-7 days at least 9% of babies, all but one of whom were breast fed, were visibly jaundiced. The frequency of prolonged jaundice (breast milk jaundice) was 3.8% of breast fed babies at 3 weeks and zero by 7 weeks. The proportion of babies receiving phototherapy was 2.2%.