|Year : 2015 | Volume
| Issue : 1 | Page : 50-55
Variation in the serum bilirubin levels in newborns according to gender and seasonal changes
Jyoti Bala1, Yuthika Agrawal1, Kiran Chugh1, Meenakshi Kumari1, Vipin Goyal2, Pardeep Kumar3
1 Department of Biochemistry, Post Graduate Institute of Medical Sciences, Rohtak, Haryana, India
2 Department of Respiratory Medicine, Shaheed Hasan Khan Mewati Government Medical College, Nalhar, Mewat, Haryana, India
3 Department of General Medicine, Employees State Insurance, Rohtak, Haryana, India
|Date of Web Publication||13-Apr-2015|
Dr. Yuthika Agrawal
Shaheed Hasan Khan Mewati Government Medical College, Nalhar, Mewat - 122 107, Haryana
Source of Support: None, Conflict of Interest: None
Introduction: Bilirubin is a substance that is produced during the process of hemolysis. Gender influences on neonatal illnesses and outcomes have remained a topic of debate and investigation. Empirical neonatological experience suggests that prevalence and degree of neonatal jaundice might be dependent on seasonal variation also. The aim of our study is to interpret the bilirubin levels in newborns according to gender and seasonal variation. Materials and Methods: The study was done from October 2012 to July of 2013 (differentiated by seasonal variation). A total of 1000 jaundiced newborn (500 of each sex diagnosed clinically and divided equally in summer and winter season) were studied to assess the total, direct and indirect serum bilirubin levels using colorimetry. Results: Out of total 1676 deliveries (439 were caesarean, 13 were assisted and rest were normal) during winter season and 1475 deliveries (399 were Cesarean, 14 were assisted and rest were normal) during summer season, 500 male newborn and 500 female newborn were analysed, divided equally in both seasons. Serum bilirubin was higher in males in summers and mainly comprised unconjugated bilirubin while direct bilirubin was higher in females in winters. Raised indirect bilirubin was more common in males born in summer than those born in winters (P = 041). In winters raised direct bilirubin was more common in females as compared to males (P = 0.019). Among female neonates total and indirect bilirubin was significantly raised in those born in summers (P = < 0.001 and <0.001, respectively) while direct was raised in those born in winters (P = 0.003). Conclusion: Physiological and pathologic phenomena associated with male gender must be integrated in the frame of understanding of both susceptibility and protection of the male newborn which has not been available for adequate investigation in the past. The higher temperature during the summer, with a greater influence of higher breastfeeding cause more severe hyperbilirubinemia.
Keywords: Bilirubin, gender, neonatal hyperbilirubinemia, season
|How to cite this article:|
Bala J, Agrawal Y, Chugh K, Kumari M, Goyal V, Kumar P. Variation in the serum bilirubin levels in newborns according to gender and seasonal changes. Arch Med Health Sci 2015;3:50-5
|How to cite this URL:|
Bala J, Agrawal Y, Chugh K, Kumari M, Goyal V, Kumar P. Variation in the serum bilirubin levels in newborns according to gender and seasonal changes. Arch Med Health Sci [serial online] 2015 [cited 2019 Jun 25];3:50-5. Available from: http://www.amhsjournal.org/text.asp?2015/3/1/50/154945
| Introduction|| |
Neonatal hyperbilirubinemia (NH) is associated with a variety of conditions. Hyperbilirubinemia appears in approximately 60% of the newborns at term and almost in all preterm neonates, with prevalence greater than 80%. , In the vast majority of newborns, jaundice is a benign condition. Physiological aspects that contribute to NH include increased bilirubin production, less efficient hepatic conjugation, and enhanced bilirubin absorption by the enterohepatic circulation.  In addition to physiologic jaundice, common identified pathologic causes include isoimmune hemolytic disease and glucose-6-phospahate dehydrogenase (G6PD) deficiency. ,, Moreover, several studies have revealed that in the absence of any jaundice, a total serum bilirubin (TSB) level of 12 mg/dL is extremely unlikely. , Although a safe threshold for TSB has not been defined, most physicians have adopted a TSB ≥20 mg/dL as indicating vulnerability to neurotoxicity. 
Various environmental factors influence NH. Etiologies leading to NH can carry a geographic difference as for instance, in one study, NH was shown to be more common in babies of Chinese ethnic origin than those of Indian, Malay and other origins.  In utero conditions have also been shown to influence NH. There are many different conditions that can cause elevated unconjugated bilirubin in newborns. These include hemolysis, syphilis, haemorrhage and a number of other conditions. Unconjugated bilirubin in newborns tends to be higher than the normal value for adults. The placenta is responsible for removing unconjugated bilirubin. In most cases, the normal functioning of baby's liver system will ensure that this difference in the value of bilirubin corrects itself over time. Direct bilirubin in newborns is also processed through the liver and bile system of the infant. A failure of any of these systems due to development problems will lead to increased level of direct bilirubin. 
In some cases, the baby's position in the womb may affect the level of bilirubin in newborns. There have been cases where an entanglement of the umbilical cord has lead to the development of high levels of unconjugated bilirubin in newborns. 
Gender influences on neonatal illnesses and outcomes have remained a topic of debate and investigation. Many clinically observable differences influencing NH have been reported to be subject to gender bias in the newborn: Apgar scores, pulmonary disease (respiratory distress syndrome), intravascular hemorrhage (IVH), and urinary tract infection,  but there is no consensus data regarding influence of gender on NH as such.
Empirical neonatological experience suggests that prevalence and degree of neonatal jaundice might be dependent on seasonal variation also, mainly due to the sunshine duration.  The higher temperature during the summer have also shown to contribute to the qualitative and quantitative differences found in bilirubin in this season, with a greater influence of breastfeeding and more severe hyperbilirubinemia. However, evidence-based data on this issue are scarce. 
Therefore, the purpose of this current study is its role in completing this jigsaw puzzle and to identify the differences in NH according to fetal sex and variation in seasons in our north-Indian neonatal population which have never been done before.
| Materials and Methods|| |
This observational study was performed at the Obstetrics department of PGIMS Rohtak from October 2012 to July of 2013 to include the seasonal variations. A total of 1000 jaundiced newborn, 500 of both sex diagnosed clinically divided equally in summer and winter season were taken. Eligible infants enrolled had an estimated gestational age of 37 weeks, who survived >2 days had no major anomalies, and had parental consent for study participation.
Neonates born at less than 35 weeks gestational age, having metabolic condition with basal ganglia involvement (e.g., glutaric acidaemia type II, pyruvate dehydrogenase deficiency, Hallervorden-Spatz disease More Details, neurofibromatosis type I), with asphyxia, acidosis, hypoxia, hypothermia, meningitis, sepsis were excluded from the study. These conditions show decreased albumin binding, low serum albumin concentration, or binding interfered with by drugs. Also major congenital malformations, clinical syndromes, chromosomal abnormalities or TORCH (toxoplasmosis, rubella, cytomegalovirus, herpes and syphilis) and human immunodeficiency viral were excluded.
Visual inspection of skin colour was used to detect jaundice in newborns, followed by quantitative measurement of direct, indirect and total serum bilirubin. Bilirubin was analyzed with a diazotized sulfanilic acid reagent method on second day of birth. 
| Results|| |
Out of total 1676 deliveries 439 were Cesarean, 13 were assisted and rest were normal during winter season and 1475 deliveries occurred in summer season, out of which 399 were by Cesarean section, 14 were assisted deliveries and rest were normal vaginal deliveries.
Mean total, direct and indirect serum bilirubin level of newborns born in winters was 11.31 ± 2.84 mg/dl, 0.64 ± 0.38 mg/dl and 10.68 ± 2.78 mg/dl, respectively, while in those born in summers was 12.40 ± 4.69 mg/dl, 0.60 ± 0.46 mg/dl and 12.09 ± 4.6mg/dl respectively. Thus total and indirect bilirubin was higher in newborns born in summers as compared to those born in winters (P < 0.001). [Table 1] demonstrates variation in NH according to season.
The values of mean, total and indirect bilirubin was slightly higher in males (12.27 ± 4.39 mg/dl and 11.66 ± 4.25 mg/dl, respectively) as compared to females (11.74 ± 3.41 mg/dl and 11.11 ± 3.41 mg/dl, respectively) but mean direct bilirubin was slightly higher in females (0.63 ± 0.35 mg/dl) in comparison to males ( 0.61 ± 0.48 mg/dl), though these differences were not statistically significant. [Table 2] demonstrates the difference in NH according to gender. Thus taking both seasonal and gender variations together, serum bilirubin was higher in males in summers and mainly comprised of unconjugated bilirubin while direct bilirubin was higher in females in winters.
Mean direct bilirubin in females during winter was 0.69 ± 0.47 mg/dl and in males was 0.59 ± 0.26 mg/dl only. This value suggests that direct bilirubin was more common in females as compared to males and was found to be statistically significant ( P = .019). While indirect and total bilirubin level in males were 10.94 ± 3.01 mg/dl and 11.51 ± 3.14 mg/dl respectively, while in females indirect and total bilirubin level were found to be 10.43 ± 2.53 mg/dl and 11.12 ± 2.54 mg/dl, respectively. Although these values were higher in males as compared to females, they were not statistically significant. [Table 3] and [Figure 1] demonstrates these seasonal variations in NH in male and female neonates.
|Figure 1: Hyperbilirubinemia in male and female neonates during winter season|
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|Table 3: Variation in neonatal hyperbilirubinemia according to gender in winter and summer season|
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During summer total, direct and indirect bilirubin in males was 13.04 ± 5.29 mg/dl, 0.64 ± 0.63 mg/dl and 12.39 ± 5.13 mg/dl, respectively. In females total, direct and indirect bilirubin was 12.37 ± 4.04 mg/dl, 0.57 ± 0.17 mg/dl and 11.8 ± 4.02 mg/dl. Hence hyperbilirubinemia is more in males compared to females during summer. [Figure 2] shows variations in NH in male and female neonates in summers.
|Figure 2: Hyperbilirubinemia in male and female neonates during summer season|
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Indirect bilirubin level were found to be higher in male neonates born in summer than those born in winter and statistically significant (P = 0.041), while the value of direct and total bilirubin levels were also found to be higher between the same groups but not significant. [Figure 3] demonstrates variations in NH in male neonates in winters and summers.
|Figure 3: Hyperbilirubinemia in male neonates during winter and summer season|
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Total and indirect bilirubin level were higher in females born in summer than those born in winter (P < 0.001) while direct bilirubin was found to be higher in females born in winter when compared to those in summer (P = 0.003). [Figure 4] demonstrates variations in NH in female neonates in winter and summer season.
|Figure 4: Hyperbilirubinemia in female neonates during winter and summer season|
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| Discussion|| |
Although NH has been thoroughly evaluated, there are only few reports on the manifestations within different etiologies. There are often multiple reasons causing NH and combined etiologies may result in greater severity of NH.  Here we have evaluated gender and seasonal differences as the possible etiological factor in NH which as to our knowledge, has never been done before.
Season can act as an independent etiological factor of NH, as in our study total and indirect bilirubin was higher in newborns born in summers as compared to those born in winters (P < 0.001). Indirect bilirubin levels were found to be higher in both male and female neonates born in summer than those born in winter in respective gender (P = 0.041for males, <0.001 for females). On the other hand, total bilirubin levels were higher only in females born in summer as compared to those born in winter (P < 0.001). Although the value of direct and total bilirubin levels were also found to be higher in males born in summer as compared to those born in winters but this was not significant. The possible reason can be that higher temperature during the summer could contribute to the qualitative and quantitative differences found in NH.  Gonzαlez et al. also observed more pathologic hyperbilirubinemia during the fall and less in winter, but in their study, these differences between seasons were not statistically significant. This difference found in summer by them was due to breast milk jaundice. In summers neonates tends to drink more of breast milk and this breast milk inhibits UDP-GT leading to rise in unconjugated bilirubin and more infants with maximum serum bilirubin >20 mg/dl and more admissions from external delivery rooms. 
It is also been proved that high unconjugated bilirubin levels gives protection against oxidative stress. Recent studies also suggest a beneficial action of bilirubin due to its protective effect from secondary oxidants. Since the newborn infant is very sensible to oxidative damage, it is possible that seasonal variation of bilirubin level during the first few days of life may influence further development and susceptibility to pathological manifestations. So rise of serum bilirubin level during the first 24 hours of life has been shown to depend on season of birth (more stress in summers). 
Regarding gender influence, we found hyperbilirubinemia is more in males as compared to females during summer though it was not significantly high. The study done by Veni, demonstrated that the deficiency in enzyme system maturation or secondary affects may result from higher acuity of illness in newborn males which may influence the generation, metabolism, and elimination of serum bilirubin in these newborns. Gender divergent glucoronidation rates were observed in humans and gender difference in UDP-GT mRNA has also been observed in rodents.  A significant association between G-6-PD deficiency and NH was also shown in males in another study but not in female neonates. In this study male neonates had a considerably higher incidence of neonatal jaundice than did female neonates and there was an inverse dose-response in relation between G-6-PD activity and neonatal jaundice among male neonates.  Study conducted by Muraca and Fevery revealed that the activity rate of this UDP-GT was higher in adult female rats than male rats and in their studies gonadectomy decreased enzyme activity in females and increased it in male rats suggesting the sex hormones may be an important regulator of conjugation,  thus increasing bilirubin conjugation and leading to less NH in females. Another study also suggested the serum levels of unconjugated bilirubin was lower in female during reproductive age than in male, this might be due to estro-progesterone and testerone effect on conjugation rate because testosterone downregulates UDP-GT, whereas combination of estrogen, progesterone enhances enzyme activity.  These effects might be prevalent in neonates also, leading to same results.
Thus, higher bilirubin in the hospitalized male infant may also be a reflection of various maturational and genetically determined pathophysiological characteristics in males which may be physiologically beneficial. Unfortunately, such an effect can only be supported in the future through the analysis of a more comprehensive data set. 
Several other clinical factors like Apgar scores, pulmonary disease (respiratory distress syndrome), IVH, and urinary tract infection have been shown to subject to gender bias in the newborns. These factors also indirectly contribute to hyperbiliribenemia. These are reported more common in males. This male disadvantage or the Y-chromosome effect has been postulated to be responsible for these differences. The role that various gender-biased biologic mechanisms contribute to the observed male disadvantage can only be speculated. Dysfunction of the placenta can be a factor, as described in association with male fetus pregnancies. In addition, a higher metabolic rate in the male fetuses may be another contributing factor. This theory is enforced by the fact that XY blastocysts and embryos grow at an accelerated rate when compared with XX chromosome bearers. An inverse relationship between lifespan and metabolic rate has been established and may reflect significant differences in associated physiological mechanisms.  In a previous study the phenomenon of protection from oxidation stress as discussed earlier was shown to be much more marked in males than in female newborn infants. 
In our study direct bilirubin is more common in females born in winters as compared to males born in winters (P = 0.019) and to females born in summers (P = 0.003). The rise of serum bilirubin in winters is higher, can possibly due to less sunshine duration,  and due to the fact that children born in the winter period are more exposed to other contributing agents, such as infections leading to inflammation of the liver-biliary system and obstructive jaundice, thus increasing direct bilirubin. The reason of more incidence of direct bilirubin in females is unknown and beyond the scope of our study.
In our study out of total 1676 deliveries 439 were Cesarean in winter season and of 1475 deliveries in summer season, 399 were by Cesarean section. Increased Cesarean section (c/s) rates in summers, may also be a reason contributing to an increased frequency of neonatal hyperbilirubinemia. , Type of the anesthesia used for Cesarean section and delivery mode may also affect the risk for hyperbilirubinemia. ,, However, in some other studies lower bilirubin levels after Cesarean section are reported and are supposedly explained by placental transfusion or timing of cord clamping. , Reports investigating the relation between anesthesia type, anesthetic agent, and hyperbilirubinemia have shown different results.  Bupivacaine hydrochloride is a safe and efficient agent for maternal segmental epidural anesthesia. However, it may cause neonatal jaundice by placental passage of anesthetic agent which binds to fetal red blood cell membranes and decreases erythrocyte half-life. 
Tioseco et al. reported high peak serum bilirubin in males with low birth weight (weight, 1500-2499 g) when compared to females, in addition to association with other risk variables such as sepsis and IVH. The difference in IVH prevalence is worth further analysis and could be attributed to differences in severity of illness in the male group.  Indirectly it can be understood that, when there is indirect bilirubin in infants, it is highly likely that the infant will suffer from malnourishment (less birth weight). In such a situation, a surgical birth may be prescribed, as the chances of the child surviving a normal birth will be reduced,  thus increasing a chance of hyperbilirubinemia as type of the anesthesia used for c/s and delivery mode may also affect the risk for hyperbilirubinemia, ,, as already said.
The small diffverence in bilirubin noted between male and female infants, although statistically significant, may appear clinically trivial. However, the results of this study rekindle the interest in a topic studied in the past, namely the super-female newborn, albeit with a new application. The study has some limitations because it did not correlate peak bilirubin levels with initiation and type of feed, or with the use of phototherapy, and the fact that in the country like India care-givers may be influenced by gender in their management of these infants. Moreover, hematocrit levels were not controlled in this study. Also there can be difference in bilirubin by the discrepancy in mortality rates between males and females. More of the sicker males may have died in the first 2 days curtailing their opportunity to demonstrate their peak bilirubin levels.
| Conclusion|| |
In summary, gender and seasonal influences on neonatal illnesses and outcomes remains a topic of debate and investigation. The value of this current study is in its role in completing a larger and more complicated jigsaw puzzle of gender and seasonal variations, which has never been done before. The result of our study may provide information to improve education for nurses in identifying male sex and summer season as additional risk factors in the development of NH and the prevention of hyperbilirubinemia readmissions and also the mortality associated with it. Physiological and pathologic phenomena associated with male gender must be integrated in the frame of understanding of both susceptibility and protection of the male newborn which has not been available for adequate investigation in the past. The higher temperature during the summer and increased c/s rates could contribute to the qualitative and quantitative differences found in this season in NH manifestations, with a greater influence of frequency of breastfeeding resulting in higher indirect bilirubin while more incidences of infections in winters can contribute to inflammation of liver and biliary system and more of direct bilirubin.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]