Exposure to high levels of stress hormones during the last trimester of pregnancy can lower a boy’s IQ before birth, a new study suggests.
Surprisingly, cortisol levels in the blood did not correlate with the girls’ IQ scores, but higher cortisol levels in the urine improved their IQ scores.
The results highlight the important role of cortisol in independent fetal development in boys and girls.
When a woman becomes pregnant, her levels of cortisol, a steroid hormone released in response to stress, naturally increase. It is essential for a baby’s healthy development and has a positive impact on his or her brain development.
However, researchers have found that high hormone levels during the last three months of pregnancy may affect a seven-year-old boy’s IQ score.
To study the impact of cortisol on cognitive function in children as they grow, researchers analyzed cortisol levels in 943 pregnant women during the last trimester of pregnancy and their children’s IQ test data when they were 7 years old.
They found that pregnant women carrying boys had lower levels of cortisol in their blood than those carrying girls.
However, boys who were exposed to higher levels of cortisol in the womb scored lower on intelligence tests at age seven. And the girls seemed unaffected.
Researchers at Denmark’s Odense University said their findings suggest boys “may be more exposed to cortisol before birth” than girls.
A previous study by the same research team found that children aged one to three years had better speech and language skills when their mothers had higher cortisol levels later in pregnancy.
The study found that boys whose mothers experienced high levels of stress spoke more words between 12 and 37 months of age, while girls understood more words between 12 and 21 months of age.
Dr. Anya Wenger-Dreyer, lead author of the study, said: “While our previous research showed that prenatal cortisol exposure is positively associated with language development, in this study, prenatal cortisol exposure was negatively associated with IQ scores. This may mean that “high prenatal exposure may have temporary effects on children’s cognitive development. It should also be noted that in our previous study, toddlers’ vocabulary size was self-reported, whereas children’s IQ in this study are evaluated by trained psychologists.”
Another study also found that children exposed to high levels of cortisol were more likely to develop behavioral problems and stress-related illnesses later in life.
Meanwhile, experts have previously said that women who experience stress during pregnancy are twice as likely to give birth to a girl.
The findings were presented at the 26th European Congress of Endocrinology in Stockholm from May 11 to 14.
