Association of Maternal Hair Cortisol Level with Neonatal Facial Pain Expression Based on Newborns’ Gender

Abstract

Introduction: Mother's mental and physical conditions during pregnancy affect the development of fetus. This study aimed to investigate the role of neonates' gender in pain responses and its association with maternal stress during pregnancy and programming. Materials and Methods: This study was conducted on 105 neonates (53 females and 52 males) born in Gorgan, Iran. The pain stimulus was intramuscular injection of vitamin K, a routine procedure for infants at birth. The first painful injection was performed for all children under the same conditions. The neonatal infant pain scale was used to assess pain intensity in newborns. Maternal stress during pregnancy was evaluated by measuring hair cortisol levels. Statistical analysis was done using Kolmogorov-Smirnov, independent t-test and Pearson correlation tests. Results: Mean pain intensity score before, during and after injection was not significantly different between male and female newborns. Mean pain score during injection was significantly higher in male neonates whose mothers had high cortisol levels compared to male neonates whose mothers had normal cortisol levels (P-value = 0.01). Conclusions: These data indicate gender indifferences in response to pain at birth and imply the differential effect of maternal hair cortisol levels on pain score of male neonates.