Background: Hyperbilirubinemia is the most common abnormal physical finding in the first week of life and is observed in approximately 60% of term infants and 80% of preterm infants (Stoll and Piazza, 2007).
     Melatonin stimulates secretion of corticosterone which decreases calcium absorption by bones. Phototherapy leads to inhibition of pineal gland via transcranial illumination, resulting in a decline in melatonin level and as a result, hypocalcemia develops (Karamifar et al., 2002).
 The aim of the study was to determine the effect of covering the head of infants during phototherapy on phototherapy induced hypocalcemia in jaundiced newborns.
Methodology: We conducted a comparative case control study at  neonatal intensive care unit of Al Hussein hospital,(Al Azhar University in Cairo) starting from April 2014 to December 2014.This study included 100 full term neonates with symptoms, signs and laboratory findings of neonatal indirect hyperbilirubinemia treated with phototherapy. Apart from jaundice, their physical examination was completely normal.
      Calcium level was measured on admission and after 48 hours of phototherapy.
      We designed a hat with a dark color that can cover all the head including the occipital area, ears and neck to prevent passage of light. The hat was used from admission and for 48 hours of treatment with phototherapy.
      Neonates were randomized and divided into two groups: group (A) 50 infants under the routine phototherapy without hats and group (B) 50 infants using hats that cover occipital area. A comparative study was made between these groups to determine the effect of hat in prevention of phototherapy induced hypocalcemia.
Results: In this study, we found that 19 infants (19 %) of both groups developed hypocalcemia after 48 hours of starting phototherapy. There was significant statistical difference between the incidence of hypocalcemia in group A (without hats) which were 13 infants (26%) and group B (with hats) which were 6 infants (12 %)(p= 0.031).
Conclusion: We conclude that, phototherapy induced hypocalcaemia can be prevented by covering newborn head during phototherapy.
Recommendations: We recommend that neonates should be regularly evaluated for total serum calcium levels 48 hours after continuous exposure to phototherapy and should be managed accordingly; also all neonates with phototherapy should cover their heads using hats during treatment to prevent phototherapy induced hypocalcaemia.