Stressed Out Pregnant Mothers More Likely to Have Girls

Cortisol may play a role in fetus sex determination

Scientists from the University of Granada used hair samples to monitor cortisol in a cohort of over 100 pregnant women and made a fascinating discovery: Women experiencing stress before and during conception are twice as likely to give birth to a girl than a boy.

Cortisol is a steroid hormone that is used as an indicator of stress levels. It is commonly measured in the blood, saliva, or urine, but analyzing cortisol deposits in hair can serve as a tool to track cortisol levels historically over time.

The team of researchers obtained hair samples from participants from before conception to week 9 of their pregnancies to identify if the stress was a determinant of the baby’s sex. They found that mothers of girls had nearly double the amount of hair cortisol concentrations than mothers of boys.

“The results we found were surprising, as they showed that the women who had given birth to girls presented higher concentrations of hair cortisol in the weeks before, during, and after the point of conception than those who had boys,” said study lead María Isabel Peralta Ramírez.

The study represents one of the first in the field to examine the complex physiological connections between stress and sex…