London – Women who suffer from stress during pregnancy are more likely to have a girl, research suggests.
A study found that 60 percent of mothers-to-be who felt overwhelmed, anxious or depressed went on to have a female baby.
More than two-thirds of women who showed physical signs of stress, like high blood pressure and comfort eating, gave birth to girls. The findings do not suggest the pressures of everyday life can change a baby’s sex in the womb.
However, experts believe anxious women are less likely to achieve a successful pregnancy with a boy as male foetuses are more vulnerable to stress hormones entering the womb.
Although many stressed women give birth to girls, they may have had failed pregnancies with boys before – perhaps in the very early stages before they even realised they were pregnant.
Researchers in the US split 187 women into three groups – those having healthy pregnancies, those showing psychological signs of stress and those with physical signs. In the group of psychologically-stressed women, only 40 percent gave birth to a boy.
Among those who showed physical signs of stress, almost 70 percent gave birth to girls.
Study lead author Dr Catherine Monk said: "We have known for a while that males are more vulnerable than females in the womb. This study suggests that women’s mental well-being and stress levels in pregnancy not only matter for them but could impact the next generation."
To determine stress levels, researchers questioned women and fitted them with a blood pressure cuff. One in six were psychologically stressed. For every two boys born in this group, three girls were born.
Another one in six showed signs of physical stress. For every four boys born among these women, nine girls were born. The study, carried out at the New York-Presbyterian/Columbia University Irving Medical Centre, suggests that girls may be better at withstanding the biological effects of stress in the womb.
Male embryos, which do not cope as well, might fail to implant or be lost in an early miscarriage.
Researchers also found that the sons of stressed mothers are more likely to be born prematurely.
However the study showed social support may help to prevent premature births and the reduction in boys. Women who said they had people they could talk to and rely on for help were more likely to give birth to a boy.
Previous research has shown that female foetuses are tougher and more likely to survive. The link between maternal stress and baby gender has been identified before. Birth rates of boys fell in the US after the September 11 terror attacks in 2001 and the assassination of President Kennedy in 1963.
The new study was published in the journal Proceedings of the National Academy of Sciences.