CHICAGO - Parents looking for the one single move they can make that will guarantee a healthy outcome for their baby are out of luck.
There is no silver bullet to producing an optimal outcome when it comes to human infants, said Katie Hinde, an assistant professor of human evolution and biology at Harvard University. Hinde was one of several speakers at a 14 February session on babies and healthy development at the AAAS Annual Meeting.
Scientists are beginning to illuminate how aspects of growth and development combine to make healthier babies, and they're finding that it's a complex process that begins long before birth and can be affected by a wide variety of factors.
Primate studies of marmoset monkeys and humans have shown that a mother's early experiences, starting during her own fetal development, can act as a powerful imprint on the placenta. That's the organ that delivers blood, nutrients and other factors from the mother to her fetus. "The fetal experience [of] the mother has a really important impact on her reproductive life when she becomes an adult," said Julienne Rutherford, an assistant professor in the Department of Women, Children and Family Health at the University of Illinois at Chicago.
That early experience and other factors -- including genetics, health care and nutrition -- all interact to affect the growth and development of the placenta, which in turn affects the growth and development of the fetus.
A fetus can also have an effect on its mother, influencing the development of mammary glands, for instance. That may explain some of the differences researchers have seen in the milk produced by mothers, said Hinde.
"There's been this myth that mother's milk is pretty standard," Hinde said, but it can differ for each child. A female infant rhesus macaque, for example, receives milk that is higher in calcium than what her older brother would have gotten. That extra calcium may facilitate faster skeletal development in the young females, which could allow them to reproduce at a younger age than their male siblings.
More importantly for humans, though, discovering the differences in human milk could enhance formulas for babies or even make it possible to match donor milks in neonatal units to improve outcomes for these vulnerable infants, Hinde said.
Studies of young men in the Philippines indicate that certain hormones change when fatherhood begins. | Fe Largado, taken with participant consent
Humans have a unique life history in which they produce offspring that remain dependent on their parents for a long time. Parental care can have a huge impact on human development. "From a human evolutionary perspective, we know that mothers have been cooperating with someone to make this possible, and fathers are one of those potential candidates. But anthropologists have raised a lot of questions about whether fathers were particularly reliable" and what they might have been doing as part of their fatherhood, said Lee Gettler, an assistant research professor in the department of anthropology at the University of Notre Dame in South Bend, Indiana.
If human fathers have a history of helping to raise their offspring, then natural selection should have worked to change the male's physiology to adapt to fatherhood, Gettler explained. And there is evidence from Gettler's studies of young men in the Philippines that certain hormones change when fatherhood begins -- testosterone decreases and prolactin increases. Similar changes happen in other species in which fathers care for their young.
But quality of care also matters, said Robin Nelson, an assistant professor of anthropology at Skidmore College in Saratoga Springs, New York. "When kids do better, what is it that their caretakers are doing?" she asked. Nelson is beginning to tease out those factors by studying children in orphanages and family settings in the Caribbean.
She noted that the caretaker at one children's home she works with has been able to put a number of psycho-social support mechanisms into place that are absent not only in other facilities but also in the homes of children who live with family and extended family. "This has made quite a difference," she said.