(Reuters) - Babies in the womb show evidence of learning by their 34th week, three weeks earlier than previously thought, new research has found.

"It really pushed the envelope" in terms of how early babies begin to learn, lead researcher Charlene Krueger, associate professor at the University of Florida's College of Nursing, said on Thursday.

The study, published in the journal Infant Behavior and Development, followed 32 women from their 28th through 38th weeks of pregnancy in an investigation to pinpoint when the ability to learn emerges.

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 fetuses’ heart rates were monitored at 32, 33 and 34 weeks as they listened to a recording of a female stranger recite the rhyme.

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

Krueger said a decelerating heartbeat has long been associated with a fetus recognizing something familiar, compared with an accelerated heartbeat response to a novel sound or experience.

"We cautiously concluded, because it was not statistically significant, that learning emerged by 34 weeks gestational age," she said.

At that point, the mothers stopped reciting the rhyme to their babies who were tested again at 36 and 38 weeks.

"At 38 weeks we confidently concluded the fetus could remember the rhythm of that nursery rhyme, which was four weeks after the mother stopped reciting the rhyme," Krueger said.

"The deeper and more prolonged response (at 38 weeks), the more confident I felt that learning had gone on," she said.

Krueger said the findings have implications for the care of pre-term babies in neonatal units. She said she next wants to experiment with placing recordings of the mothers’ voices in the babies’ cribs so they will benefit from positive impacts of their mothers’ voices.

“What it really shows is how sophisticated the interaction is between a mother and her infant,” she said.

(Editing by David Adams and Matthew Lewis)