For babies born prematurely, being held in their parents' arms, directly against their skin, for a few hours per day is believed to enhance development. Now, new research that followed children until age 10 suggests that the benefits of such skin-to-skin contact may be longer-lasting than previously thought.

In the study, the researchers asked 73 mothers to give their babies skin-to-skin contact for one hour per day for two weeks.For comparison, the researchers also looked at 73 premature infants who only spent time in an incubator — the standard form of care for premature infants.

At age 10, the children who had received maternal contact as infants slept better, showed better hormonal response to stress, had a more mature functioning of their nervous system and displayed better thinking skills.

The results show that adding "maternal-infant contact in the neonatal period has a favorable impact on stress physiology and behavioral control across long developmental epochs in humans," Ruth Feldman, a professor of psychology at Bar-Ilan University in Israel, and her colleagues wrote in their study, published Jan. 1 in the journal Biological Psychiatry. [7 Ways Pregnant Women Affect Babies]

About 12 percent of infants in the United States and other industrialized societies are born prematurely, which is defined as at least three weeks before their due date. Rates of preterm birth are significantly higher in developing countries. Premature babies face a higher risk of lifelong problems such as intellectual disabilities, breathing problems, hearing loss and digestive problems, according to the Centers for Disease Control and Prevention.

Studies have suggested that premature birth disrupts brain development and the maturation of certain body systems that are sensitive to human contact and the stimulation normally provided by the mother’s body, the researchers said. These systems — which include circuits that regulate stress response, heart rhythms and sleep-wake cycle — also have been shown to be sensitive to contact in animal studies.

Therefore, by holding premature babies in parents' arms, doctors hope to recreate the environment in which infants would have developed if they had not been born prematurely. Previous studies have found the treatment to be beneficial for premature babies, but it was unclear how long the effects would last, the researchers said.

Skin-to-skin contact between parent and baby is sometimes called "kangaroo care," for its likeness to the way kangaroos hold a young one in a pouch, close to the parent. The care was originally studied as a way to help premature babies in Colombia, where access to incubators was scarce. Using this method, low-weight babies were kept warm by their mothers' body heat.

In the new study, mothers who performed the kangaroo care reported having a deeper and more caring relationship with their children than mothers who did not, the researchers found.

Physical contact with babies is essential for their physical and psychological development, the researchers said.

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