Babies in the womb begin to respond to the rhythm of a familiar nursery rhyme by 34 weeks gestational age and are able to remember a set rhyme just before birth, according to new research by the University of Florida. The study also highlights the important role of the mother’s voice in the baby’s learning capabilities.
For the study, published in the journal Infant Behavior and Development, pregnant women recited a rhyme to their unborn babies three times a day for six weeks, starting at 28 weeks of pregnancy, the beginning of the third trimester.
“The mother’s voice is the predominant source of sensory stimulation in the developing fetus,” said nursing researcher Charlene Krueger, an associate professor in the UF College of Nursing.
“This research highlights just how sophisticated the third trimester fetus really is and suggests that a mother’s voice is involved in the development of early learning and memory capabilities. This could potentially affect how we approach the care and stimulation of the preterm infant.”
The researchers recruited 32 women (ages 18 to 39) who were in the 28th week of their first pregnancy. Overall, 68 percent of the women were white, 28 percent were black, and four percent were of another race or ethnicity. The participants were randomly assigned to either an experimental or a control group.
From 28 to 34 weeks of pregnancy, all mothers in the study recited a particular passage or nursery rhyme twice a day and then came in for testing at 28, 32, 33, and 34 weeks’ gestation. Then to determine whether the fetus could remember the pattern of speech, all mothers were asked to stop speaking the passage at 34 weeks. Then the fetuses were tested again at 36 and 38 weeks.
To test the babies’ responses, researchers used a fetal heart monitor to record heart rate and detect any changes. A small heart rate deceleration in the fetus is considered a sign that the baby is familiar with a stimulus.
During the experiment, the fetuses were played a recording of the same rhyme their mother had been reciting at home but spoken by a female stranger. Those in the control group heard an unfamiliar rhyme spoken by a stranger. This was to determine if the fetus was responding simply to its mother’s voice or to a familiar pattern of speech, said Krueger.
The findings showed that the fetus’ heart rate began to respond to the familiar rhyme recited by a stranger’s voice by 34 weeks of gestational age — at this point the mother had spoken the rhyme out loud at home for six weeks. The babies continued to respond with a small cardiac deceleration up to four weeks after the mother had stopped reciting the rhyme until about 38 weeks.
At 38 weeks, there was a statistically significant difference between the two fetus groups — the experimental group who heard the original rhyme responded with a deeper and more sustained cardiac deceleration, whereas the control group who heard a new rhyme experienced a cardiac acceleration.
“This study helped us understand more about how early a fetus could learn a passage of speech and whether the passage could be remembered weeks later even without daily exposure to it,” Krueger said.
“This could have implications to those preterm infants who are born before 37 weeks of age and the impact an intervention such as their mother’s voice may have on influencing better outcomes in this high-risk population.”
Source: University of Florida