New Scientist reports:

Male fetuses ignore their mothers’ response to stress – unlike females, which are very sensitive to it. The finding could lead to better treatments for male fetuses at risk of premature birth.

It is known that when a pregnant woman produces the stress hormone cortisol, it can cross the placenta. But it has been unclear how this affects fetal development, and whether female and male fetuses respond differently to the hormone.

During an asthma attack, high levels of cortisol are released. So Vicki Clifton and colleagues at the University of Adelaide in South Australia investigated the effect of cortisol on fetuses by following 123 asthmatic women and 51 healthy women during their pregnancies, recording the severity of each woman’s asthma and her medication at 12, 18 and 30 weeks of pregnancy.

Forty-five minutes after the women gave birth, Clifton and her team measured the cortisol in their umbilical cord blood and analysed the placenta for the expression of genes related to stress response. She also recorded the newborn’s sex and birth weight.
Stressful information

Baby girls born to women with moderate to severe asthma had higher levels of cortisol in their cord blood – an average of 245 millimoles per litre – compared with girls born to controls and mildly asthmatic women, who averaged 202 and 209 millimoles per litre respectively.

However, no difference in cortisol levels was observed in baby boys born to either group.

To find out more check out New Scientist.