GAINESVILLE, Fla. - Whether it's Mozart, Beethoven or Shakespeare, pregnant mothers have been known to expose their babies to many forms of auditory stimulation. According to a new study done at the University of Florida, all a baby really needs is the sound of his or her mother's voice.
The 'Infant Behavior and Development' journal recently published information showing that babies in the uterus begin to respond to the rhythm of a nursery rhyme by 34 weeks of pregnancy and are capable of remembering a set rhyme until just prior to birth.
Nursing researcher Charlene Krueger and her team studied pregnant women who recited a rhyme to their babies three times a day for six weeks. The women began reciting rhymes at the start of the third trimester.
"The mother's voice is the predominant source of sensory stimulation in the developing fetus," said Krueger. "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 32 participants were between 18-39 years old, spoke English as a primary language and were pregnant with their first baby.
After being selected, Krueger separated the mothers into two groups: the experimental group and the controlled group.
From 28 to 34 weeks of pregnancy, all mothers in the study recited a passage or nursery rhyme out loud twice a day.
Throughout that time, the fetuses were tested with a fetal heart rate monitor to evaluate for the emergence of learning.
To determine if the fetus could remember the pattern of speech, all mothers were asked to stop speaking the passage at 34 weeks. The fetuses were tested again at 36 and 38 weeks to test memory.
Researchers interpreted a small heart rate deceleration in the fetus as an indicator of learning or familiarity with a stimulus.
At testing, the fetuses in the experimental group 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 a different rhyme also spoken by a stranger. This was to help determine if the fetus was responding simply to its mother's voice or to a familiar pattern of speech.
The researchers found that the fetus' heart rate began to respond to the familiar rhyme recited by a stranger's voice by 34 weeks of gestation once the mother had spoken the rhyme out loud at home for six weeks.
They continued to respond with a small cardiac deceleration for as long as four weeks after the mother had stopped saying the rhyme until about 38 weeks.
At 38 weeks, there was a statistically significant difference between the two groups of fetuses.
Results concluded the fetuses who listened to the strangers' recited rhymes responded with a more sustained cardiac deceleration and the fetuses who heard a new rhyme by strangers responded with a cardiac acceleration.
Further research is needed to more fully understand how ongoing development affects learning and memory, Krueger said.
Her aim is to recognize how this type of research can influence care in the preterm infant and their long-term outcomes.
"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."