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The stressful condition of the expectant mother affects the sex of the baby
Last reviewed: 02.07.2025
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If a woman experienced severe stress during the period of planning or conceiving a child, she has an increased probability of giving birth to a girl. This conclusion was voiced by Spanish scientists representing the University of Granada.
There are many known factors that directly or indirectly affect the course of labor, the birth of a child, and the quality of fetal development. In particular, a woman's severe psychological stress can cause postpartum depression, lead to the need for auxiliary obstetric actions during labor, change the onset of the lactation period, and affect the baby's neuropsychic development during the first six months after birth.
In their new study, the scientists asked themselves: is there a connection between stress experienced not during pregnancy, but before it, and the sex of the future baby? Representatives of the Center for the Study of Psyche, Brain and Behavior at the University of Granada analyzed hair for the content of the glucocorticoid hormone cortisol. More than a hundred women with confirmed pregnancy up to the ninth week were examined. In addition to the tests, the women underwent psychological testing.
An analysis of the cortisol level in the biomaterial taken at different periods of the first trimester of pregnancy demonstrated the content of the corticosteroid hormone over the past three months (in one month, hair grows by approximately 10 mm). In this way, scientists were able to cover the period both before and after conception. The results showed that the concentration of the hormone in the hair of women who subsequently gave birth to girls was 2 times higher than in women who subsequently gave birth to boys.
How can this situation be explained? Scientists suggest that perhaps the stimulation of the stress mechanism, which includes the activity of the hypothalamus, pituitary gland and adrenal glands, and increases the production of cortisol, affects the level of sex hormones during conception. It is a known fact that the sex of the future baby is influenced by testosterone, the level of which increases during prenatal stress.
The second version that can explain the situation is as follows: male reproductive cells containing the X chromosome, which determines the female gender of the baby, more easily overcome the barrier of cervical mucus in difficult conditions. If the expectant mother experiences severe stress and, as a result, hormonal changes occur, then spermatozoa with the X chromosome have a greater chance of reaching the egg.
Be that as it may, the researchers confirmed the link between stress and the sex of the child, but only if this stress occurred immediately before or during conception. The exact mechanism that determines this process is still unknown.
Full details of the study are available on the Universidad de Granada website