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Stress hormones during pregnancy may affect a child's IQ

Recent research presented at the 26th European Congress of Endocrinology in Stockholm has shed light on how stress hormones during pregnancy, specifically cortisol, might affect the intellectual development of children differently based on their gender.

The study found a significant difference in how cortisol and its byproduct cortisone influence boys and girls by age 7.

Stress hormones in pregnancy and its effects on fetal development

Cortisol, a key stress hormone and steroid crucial for managing stress in the body, naturally rises during pregnancy and plays a vital role in fetal development. Interestingly, women carrying female fetuses generally have higher levels of this stress hormone than those carrying males.

The placenta, through an enzyme called 11β-hydroxysteroid-dehydrogenase type 2 (11β-HSD2), regulates the amount of cortisol reaching the fetus by converting it to its inactive form, cortisone, effectively moderating the impact of stress hormones on the developing child.

Pregnancy stress and child’s IQ

In the Odense Child Cohort, researchers at Odense University Hospital in Denmark gathered and analyzed data from 943 pregnant women and their children.

They specifically looked at cortisol and cortisone levels during the third trimester and correlated these with the IQ scores of the children at age 7.

Findings revealed that boys exposed to higher levels of maternal cortisol scored lower on IQ tests, while girls showed improved scores with higher levels of maternal urine cortisone.

Gender differences in cortisol impact

“To our knowledge, this is the first study investigating the association between urine cortisone levels during pregnancy and IQ scores in children,” highlighted Dr. Anja Fenger Dreyer, the lead researcher.

She emphasized the unique approach of their research, which included separate analyses for boys and girls and considered both urine and blood samples.

“Our results show that girls may be more protected by the activity of placental 11β-HSD2, whereas boys may be more vulnerable to prenatal exposure of maternal physiological cortisol,” explained Dr Dreyer.

This suggests that the enzyme’s activity might shield female fetuses more effectively from the potential negative impacts of excess stress hormones.

Effects on cognitive and language development

The research team also compared their findings with previous studies, noting differences in how prenatal cortisol exposure affects cognitive versus language development.

“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,” Dr. Fenger Dreyer continued.

She also pointed out the differences in assessment methods between studies, saying, “The vocabulary in toddlers was reported by parents in our previous study, while child IQ in this study was assessed by trained psychologists.”

Pregnancy stress and its impact on children

This study highlights the intricate influence of cortisol and cortisone — two critical stress hormones — during pregnancy on the intellectual growth of children. These hormones do not simply fluctuate; they have profound, lasting effects that vary significantly between genders.

The research particularly illuminates how these hormonal variations might hinder or enhance cognitive development in boys and girls, respectively.

Moreover, the findings spark crucial discussions regarding the distinct ways prenatal stress hormones impact male and female fetuses. It suggests that natural protective mechanisms, like the enzyme 11β-HSD2 in the placenta, might operate differently based on the fetus’s gender.

Such insights are vital as they guide future research directions, encouraging deeper exploration into how these biochemical shields operate and potentially how they can be influenced to safeguard fetal development against stress-related risks.

This opens a fascinating new chapter in developmental science, promising to unveil strategies that could enhance cognitive outcomes across both genders.


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