Research presented at the 26th European Congress of Endocrinology in Stockholm shows that high cortisol levels in the third trimester of pregnancy can negatively impact the intelligence quotient (IQ) scores of 7-year-old boys.

Surprisingly, blood cortisol levels in girls were unrelated to IQ scores, but higher urine cortisol levels did improve the girls’ scores. The results highlight the important role of cortisol in the intrauterine development of girls and boys.

Prenatal exposure to cortisol, a steroid hormone that helps the body respond to stress, is essential for fetal development and is thought to affect children’s cognitive function later in life. Cortisol levels rise during pregnancy, and pregnant women carrying a girl tend to produce more cortisol than those carrying a boy. However, the 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) enzyme in the placenta regulates the amount of cortisol reaching the fetus by converting cortisol into its inactive form known as cortisone.

Details and results of the research

Researchers at Odense University Hospital in Denmark had previously shown that children between the ages of one and three had more advanced speech and language skills if their mothers had high cortisol levels in the third trimester.

Now, in this study, researchers analyzed data on cortisol and cortisone levels of 943 pregnant women in their third trimester and IQ tests of 943 7-year-old children from the Odense Children’s Cohort. They found that pregnant women carrying a boy had lower blood cortisol levels than women carrying a girl. Additionally, boys exposed to high levels of cortisol in the womb had lower IQ test scores at age 7. Girls of the same age scored better on IQ tests when their mothers’ urinary cortisone levels were higher.

New ideas and implications

Lead author Dr. “To our knowledge, this is the first study to examine the relationship between urinary cortisone levels during pregnancy and IQ scores in children,” said Anja Fenger Dreyer. “While other studies have only examined circulating cortisol during pregnancy and child IQ, we are the first to look at urine samples as well as blood samples and to examine boys and girls separately.”

Dr. Fenger Dreyer added: “Our results suggest that girls may be more protected from placental 11β-HSD2 activity, while boys may be more vulnerable to prenatal exposure to maternal physiological cortisol.”

“Although our previous study showed that prenatal cortisol exposure was positively associated with language development, in this study prenatal cortisol exposure—”directly” through serum cortisol and “indirectly” through urinary cortisone—was negatively associated with IQ scores, Dr. Fenger Dreyer continues. did.

“This may mean that exposure to high levels of cortisol may have a temporary effect on a child’s cognitive development. It is also worth noting that, while in our previous study the vocabulary used by young children was reported by parents, in this study the child’s IQ was assessed by trained psychologists .”