A Moment of Science

Girl Fetuses Respond To Mothers’ Stress More Than Their Brothers

Scientists find that male fetuses ignore their mothers' stress signals.

Newborn baby and mother

Photo: Insight Imaging: John A Ryan Photography (flickr)

Baby boys ignore their mother's stress in the womb and continue to grow at their normal rate, but this means they may actually need more care in order to protect them from malnutrition.

Does an expecting mother’s stress affects her baby’s health?

It depends if the baby is a boy or a girl.

In this Australian study, scientists look specifically at the stress hormone cortisol. Cortisol released into the body in high doses during an asthma attack.

Over the course of 30 weeks, cortisol levels were measured in both healthy and asthmatic mothers-to-be. The severity of asthma and their respective medications were taken into account.

Forty-five minutes after birth, the study determined three things: sex, weight and cortisol levels found in the umbilical cord.

Girl infants born to asthmatic mothers showed much higher levels of cortisol. These baby girls were also significantly smaller than girls born to non-asthmatic mothers. The stress hormone tells the fetus that the mother’s nutrition levels may drop, so the baby’s body adapts accordingly.

Baby boys, on the other hand, seem to ignore this hormonal signal completely. They continued to grow at their normal rate in both asthmatic and healthy mothers, despite cortisol levels. The researchers suspect that the advantages of being large must override the risk of malnutrition, but it has yet to be determined what those advantages are.

However, the researchers hope their findings will help safeguard the health of male babies born prematurely.

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Molly Plunkett

is a journalism student at Indiana University and an online producer for A Moment of Science. She is originally from Wheaton, IL.

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