And as the foetus grows, these facial motions become increasingly complex, found the study by researchers at the University of Durham in the UK.

While it was known that foetuses could form expressions while in the womb, this new study tracked facial movements over time, LiveScience reported.

By capturing images of two foetuses periodically from 24 to about 35 weeks of gestation, the Durham team watched individual, unrelated movements progress to complex combinations, associated with recognisable facial expressions.

“What we have found for the first time is you can look at the progression of the complexity of the movements,” lead study author Nadja Reissland said.

In addition to tracking 19 total facial movements, the researchers focused on sets of movements associated with two expressions, one associated with crying, the other laughing. Over time, the movements associated with these began to appear in more complex combinations.

For the study, appeared in the journal PLoS ONE, the researchers used 4-D ultrasound images, which resemble video, to track the facial motions of two female foetuses.

At 24 weeks, foetuses were more likely to make a single movement, like a widening of the lips for example, all by itself. Then, as the weeks passed, they began combining the movements, putting, say, a lip widening movement with a nose wrinkle.

By about 35 weeks, combinations of three and four movements associated with the two expressions had surpassed single or double movements. A similar trend occurred when the researchers looked at all 19 movements.

Reissland pointed out that these facial movements don’t mean the foetuses were experiencing emotion.

“We can see the expressions which we can recognise; we can’t say whether the foetus has emotion,” she said. “They (don’t) have yet the cognition necessary to have the emotions.”

Rather, these motions are likely a form of practice, as the foetuses prepare to enter the social world, where they must form bonds with others, she said.

Foetuses also suck their thumbs in the womb and make breathing motions, both precursors for important activities once they are born, she added.

The researchers are now planning to look for other foetal facial expressions associated with anger, smiling and sadness.