Memory Forms at 30 Weeks in the Womb

July 16 -- WEDNESDAY, July 15 (HealthDay News) -- Fetuses that are only 30 weeks old may already possess short-term memory, Dutch researchers report.

"This is the next step into a better insight in the development of the fetal central nervous system," said study co-author Dr. Jan G. Nijhuis, director of the Centre for Genetics, Reproduction and Child Health at Maastricht University Medical Centre in the Netherlands. "We aim to develop an 'intra-uterine neurologic examination,' which could then be used in fetuses at risk."

Although memory is thought to develop while the baby is still in the womb, little else is known about the phenomenon.

"It is a fairly new idea to look at whether learning occurs in utero," said Dr. Russell Fothergill, an assistant professor of obstetrics and gynecology at Texas A&M Health Science Center College of Medicine and director of ambulatory care at Scott & White.

The authors recruited 93 pregnant Dutch women, and then measured fetal responses to repeated "vibroacoustic" stimulation. Their report appears in the July/August issue of Child Development.

"We used a vibroacoustic stimulator, which leads to a combined stimulus of vibration and sound," Nijhuis explained. "The stimuli were applied to the maternal abdomen above the fetal legs for a period of one second every 30 seconds. We counted the number of stimuli after which the fetus does not respond anymore."

When the fetus makes the change to no longer responding, it is "habituated"; it recognizes the stimulus as "safe."

The authors stated that habituation is a form of learning and needs an intact central nervous system.

"In its simplest form, [habituation] is related to how we think about humans learning," Fothergill said.

According to background information in the paper, the first study to look at fetal habituation took place in 1925 and involved repeated honking of a car horn. Since then, similar studies have been conducted with electric toothbrushes and door buzzers, as well as the vibroacoustic stimulator.