SINGAPORE: The results of a new study on the effect of stress during a woman’s pregnancy has found that stress appears to affect boys and girls in the womb differently.
The stress hormone cortisol is believed to be vital to a baby’s development while in the womb, with a research team from the Odense University Hospital in Denmark having previously shown that it could help with early language development.
However, the team presented new research at the 26th European Congress of Endocrinology in Stockholm earlier this month, where they showed that too much cortisol from week 27 and onward of a woman’s pregnancy could prove to be detrimental to her child later on.
“To our knowledge, this is the first study investigating the association between urine cortisone levels during pregnancy and IQ scores in children,” BBC’s Science Focus quotes the study’s lead author, Dr Anja Fenger Dreyer, as saying.
The researchers believe that a woman’s pregnancy stress may affect cognitive function by the time a child reaches the age of seven. However, due to the role of the placenta, exposure to cortisol could be different for boys and girls.
“Our results show that girls may be more protected by the activity of placental 11beta-HSD2, whereas boys may be more vulnerable to prenatal exposure of maternal physiological cortisol,” Dr Fenger Dreyer said.
More cortisol tends to be present when women are pregnant with girls. However, how much cortisol reaches the baby is controlled by an enzyme in the placenta, which ends up converting the cortisol into cortisone, another hormone, albeit an inactive one.
Boys in the fetus, however, do not benefit from this enzyme, which leaves them more vulnerable to stress hormones.
Dr Fenger Dreyer and her team measured the levels of cortisol and cortisone in 943 pregnant women, comparing these to the IQs of their children seven years later, as measured by trained psychologists. They discovered that the boys who had been exposed to higher levels of cortisol while they were in the womb had lower IQs. Moreover, when the team looked into cortisol found in urine samples rather than in the blood, they discovered that girls’ IQs were higher.
“Although our previous study showed prenatal cortisol exposure was positively associated with language development, in this study prenatal cortisol exposure – ‘directly’ by serum cortisol and ‘indirectly’ by urine cortisone – is negatively associated with IQ scores.
This may mean that the high levels of prenatal cortisol exposure might have a temporary effect on a child’s cognitive development,” she added. /TISG
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