Girls are the stronger sex and better survivors... even after just being born
The battle of the sexes begins at birth, with newborn girls more strongly genetically programmed than boys to withstand acute infection.
A new study shows newborn girls have an innate genetic advantage when it comes to potentially dangerous infections.
It is in keeping with previous research showing infant girls are hardier than boys, the findings from the Royal College of Surgeons revealed.
Newborn boys have higher rates of infection and sepsis compared with baby girls of the same gestational age. They have poorer survival rates, according to the study in the journal 'Pediatric Research'.
"While females have a recognised survival advantage throughout the entire human life cycle, this is particularly evident during the newborn period," it said.
The reasons for the advantage are due to the difference in chromosomal make-up between females, who carry two copies of the X chromosome (XX), and males who carry one X and one Y chromosome (XY).
The X chromosome had more of the genes involved in immunity than does the Y chromosome.
Catherine Greene, associate professor of clinical microbiology, said: "The phenomenon of female neonates being hardier than their male counterparts is well recognised.
"This research shows this is due to a fundamental genetic advantage which may also contribute to more effective responses to infection and disease throughout the human life cycle."
Chief researcher David O'Driscoll added: "Our findings in full-term newborn babies suggest that a similar phenomenon could be occurring in pre-term infants where gender differences can be even more marked."
This research measured the presence of a factor called IRAK1 (interleukin-1 receptor-associated kinase 1), which contributes to immunity against infection, in the umbilical cord blood of newborn babies.
Higher IRAK1 gene and protein expression was detected in the female cord blood and the authors believe this may explain in part the differences in inflammatory outcomes in infants.
In Ireland women still have a higher life expectancy than men, which is due to various factors including lifestyle.
But over the years the gap has been narrowing, with men slowly catching up with women.