In the early 1980s, two pediatricians in Bogota, Colombia, made waves around the world for a new method of caring for premature babies. The method, called Kangaroo Care, was so named because of how it resembles marsupial caregiving: A mother snuggles her baby, upright, against her bare chest for long periods of time.
The doctors developed the program in 1979 at the Instituto Materno Infantil at San Juan de Dios Hospital in Bogota. This large maternity hospital was overcrowded and understaffed and underfunded: In the special baby care unit, several babies would often share the same incubator. Infection rates were sky-high, as were abandonment rates and death rates.
To improve this dire situation, doctors Edgar Rey and Hector Martinez launched a program to get babies out of the hospital — and its germs — as soon as they were physically stable, even if they were still very small. They advised mothers to keep their baby on their chest for warmth, and to exclusively breast feed.
Rey and Martinez reported mortality rates of the 539 babies who went through this home care between 1979 and 1981. The smallest babies — those weighing between 501 and 1,000 grams — showed 72 percent survival rates, compared with 0 percent survival with the hospital’s conventional care. Nearly 90 percent of babies between 1,001 and 1,500 grams survived at home, compared with 27 percent in the hospital. And the number of babies abandoned dropped by two-thirds.
These results never appeared in a medical journal, and they are somewhat inflated because they didn’t include deaths of babies who died in the first few days of life. Nevertheless, this very appealing idea — that a mother’s touch could save her child’s life — made headlines all over the world, and UNICEF endorsed the program whole-heartedly.
People in developed countries were eager to try the new method, too, even though they didn’t have any of the problems of a strapped hospital in Colombia. Many doctors were skeptical that Kangarooing would provide much benefit in rich countries, beyond making moms and dads feel better about the experience. As two British doctors wrote in a Lancet paper — titled “Myth of the Marsupial Mother” — in 1985: “Colombia has nothing to teach developed countries about improving survival of [premature] babies but may yet help us to heal some of the psychological problems incurred by modern neonatal care.”
In the three decades since, those Colombian researchers and many other groups have published randomized, rigorous studies of Kangaroo Care, and experts continue to debate whether, and under what circumstances, it does any good. In 2011, the prestigious Cochrane Collaboration published a comprehensive review of all of the major studies to date, and seemed to confirm what Rey and Martinez had originally claimed: In resource-limited settings, Kangaroo Care significantly lowers the risk of infection, hypothermia, and death. It also increases a baby’s weight and head circumference, and the strength of the maternal bond. It’s unclear, though, whether the method’s positive effects last through a baby’s adolescence, nor whether it offers much for premature babies in developed countries.
I write this protracted introduction as a caveat to two new papers reporting that, in Colombia and Israel, respectively, the positive effects of Kangaroo Care can last for more than a decade after a baby’s birth. The studies are fascinating to me because they’re suggesting that a mother’s touch can exert a powerful influence on her child’s brain development (wow! how?). But it’s also possible, given the spotty data, that the positive effects aren’t coming from her touch, per se. So, with caveat said, on to the new studies.
The first was done by a group of Colombian and Canadian researchers who have been advocating for Kangaroo Care since the beginning. They measured brain activity of 48 teenagers in Colombia: 39 born very prematurely and 9 born at term. Of the premature group, 21 had received Kangaroo Care and 18 had received standard hospital care.
The researchers used transcranial magnetic stimulation, or TMS, in which researchers place a wand on the participant’s head. The wand contains a magnetic coil, which produces an electromagnetic pulse that passes through the person’s skull and tickles the neurons underneath. The neurons respond to that pulse, and the researchers then measure that neuronal response via EEG electrodes placed all over the scalp.
In this case, the researchers placed the wand over participants’ motor cortex, on the center of the top of the head, which is involved in motor planning. Teenagers who were born prematurely and received Kangaroo Care showed brain-wave patterns that were similar to the kids born to term, according to the study, published last year in Acta Paediatrica. In contrast, the kids born prematurely who had had standard hospital care showed a slower synchronization of brain activity.
The second study, based at a hospital in Israel, also looked at adolescents who had been born too early: 73 who had received Kangaroo Care and 73 who had been given standard incubator care. As published last week in Biological Psychiatry, the researchers found that by 10 years old, the Kangaroo babies had better responses to stress, more regular sleeping patterns, and scored higher on tests of cognitive development compared with the kids who had received standard preemie treatment.
If we assume (and, again, see caveat above) that these benefits are the direct result of skin-to-skin contact between a baby and her mother, then what could explain that?
Nobody knows for sure, but scientists have learned a lot by studying the interactions between baby rodents and their mothers. For example, early physical contact with mom affects the expression of genes related to stress hormones and social behavior in the baby animal’s brain. Conversely, depriving an infant rodent (or infant human, for that matter) of its mother leads to all sorts of behavioral and medical problems for the rest of the animal’s life. “Being a mammal therefore implies that the brain is not fully formed at birth, and maturation of systems that enable adaptive functioning in the world are gradually acquired through close contact with an alert, responsive mother,” write the authors of the new Biological Psychiatry study.
These studies of mother-baby interactions — and the descriptions of these studies in the popular press — tend to focus on these chemical mechanisms of how a mother’s touch and attention help her baby thrive. (There’s this thing called oxytocin…) What sometimes gets overlooked, though, is that this is not a one-way phenomenon. As a mother touches and influences her baby, so too does the baby touch and influence her mother. It’s the constant, back-and-forth interaction that creates the bond, and the bond that keeps a mother invested in her child’s success for many years to come.