A study of ultrasound images revealed that babies in utero start making more facial expressions during the second half of pregnancy, according to an ABC news report. Their different expressions are cute, but they also signal continuing brain development — and one expression in particular hints at the state of your emotional health.

Nadja Reisslanda, a researcher at the University of Durham in the United Kingdom and lead author of the study, found that fetuses were more likely to touch their own faces with their left hands when their mums were feeling stressed out. The gesture seems to be a self-soothing one, she says. 

To conduct her study, Reissland analysed 176 foetal mouth movements. She found that 64 percent occurred on the left side of the face, thanks to signals sent from the right side of the brain. (The right side of the brain controls the left side of the face and is also thought to play a big role in the expression of emotions.) Additionally, Reissland followed 15 mums-to-be and their unborn babies from 24 to 36 weeks gestation.

Reissland emphasises that this study only supports an association between maternal stress and foetal face-touching, and she says she looks forward to more closely exploring the link between the two.

“There is some research indicating that high levels of prenatal maternal stress might be a risk factor for developmental disorders later, since stress can alter the biochemical equilibrium in the uterus,” she adds.

The research highlights the importance of reducing maternal stress during pregnancy. Reacting to stress isn’t the only grown-up behaviour taking place in the womb. Foetuses also yawn, stretch and hiccup.

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