Babies in the womb start learning by their 34th week, three weeks earlier than researchers previously thought.

“It really pushed the envelope” in terms of how early babies begin to learn, according to lead researcher Charlene Krueger, associate professor at the University of Florida’s College of Nursing.

The study, published in the journal Infant Behaviour and Development, followed 32 women from their 28th through 38th week of pregnancy in an investigation to pinpoint when the ability to learn emerges. A typical pregnancy lasts for about 40 weeks.

Krueger had the women repeat three times out loud a set 15-second nursery rhyme, and do it twice a day for six weeks. The selected rhyme was previously unknown to the mothers. The foetuses’ heart rates were monitored at 32, 33 and 34 weeks as they listened to a recording of a female stranger reciting the rhyme.

By the 34th week, Krueger said, the heart rates of the tested foetuses showed an overall slight decline while listening to the recording, compared with a control group of foetuses whose heart rates slightly accelerated while listening to a recording of a new nursery rhyme.

Vindicating parental suspicions that their kids are precocious know-it-alls, researchers now have evidence that unborn babies can recognise their mother's voices – and retain some kind of knowledge – in their 34th week. That's up to six weeks before the kid pops out, so better watch what you say.