Boys exposed to high levels of testosterone in the foetal stage are twice as likely to experience retarded language development.
“An estimated 12 percent of toddlers experience significant delays in their language development,” said Andrew Whitehouse, associate professor at Perth’s Telethon Institute for Child Health Research.
“While language development varies between individuals, boys tend to develop later and at a slower rate than girls,” added Whitehouse, who led the study.
The finding is significant for explaining why boys’ language development differs to that of girls, said Whitehouse, the Journal of Child Psychology and Psychiatry reports.
They measured testosterone levels in the umbilical cord blood of 767 newborns before examining their language ability at one, two and three years.
The results showed boys with high levels of testosterone in cord blood were between two-to-three times more likely to experience language delay. Male foetuses are known to have 10 times the circulating levels of testosterone compared to females.
However, the opposite effect was found in girls where high-levels of testosterone in cord blood were associated with a decreased risk of language delay.
Previous smaller studies have explored the link between testosterone levels in amniotic fluid and language development. However, this is the first large population-based study to explore the relationship between umbilical cord blood and language delay in the first three years of life.