It’s a common assumption that stress during pregnancy can have negative impacts on a baby’s development. However, recent research suggests that the effects may vary between boys and girls, with girls potentially experiencing higher IQ scores as a result.
The hormone cortisol, crucial for responding to stress, is believed to play a vital role in fetal development. Previous studies from Odense University Hospital in Denmark have shown that cortisol can contribute to early language development.
Now, the same research team suggests that excessive cortisol exposure during the third trimester of pregnancy could influence cognitive function later in life, particularly as children reach seven years of age. They propose that maternal stress during pregnancy may affect boys’ and girls’ IQs differently.
Presenting their findings at the 26th European Congress of Endocrinology in Stockholm, the researchers suggest that girls may be less sensitive to cortisol exposure due to the placenta’s role. Women carrying female fetuses tend to produce more cortisol, but an enzyme in the placenta regulates its transmission to the fetus, converting it into an inactive form known as cortisone.
Conversely, boys may be more vulnerable to cortisol exposure as they lack the protective activity of this enzyme.
In their study, researchers analyzed cortisol and cortisone levels in 943 pregnant women and compared them to the IQ scores of their 943 children, assessed by trained psychologists seven years later.
The results revealed that boys exposed to higher levels of cortisol in the womb had lower IQ scores. However, researchers were surprised to find that only when cortisol was detected in urine samples – as opposed to blood samples – did girls exhibit higher IQ scores.
Lead author Dr. Anja Fenger Dreyer commented, “To our knowledge, this is the first study investigating the association between urine cortisone levels during pregnancy and IQ scores in children. While other studies have only looked at cortisol circulating in the blood during pregnancy and child IQ, we are the first to look at urine samples as well as blood samples and to investigate boys and girls separately.”
