A new study adds to a growing body of evidence that mothers’ experiences affect their babies’ chromosomes. For the first time, it also shows a gender difference — with male babies more susceptible to maternal influence. And it even implicates experiences dating back to the mother’s own childhood.
The study, led by psychologist Michelle Bosquet Enlow, PhD, at Boston Children’s Hospital, may help explain why stress can have intergenerational effects within a family. It was published last month in the journal Psychoneuroendocrinology.
The researchers enrolled 151 socioeconomically diverse mothers and their infants, all born at Beth Israel Deaconess Medical Center in Boston. The mothers completed in-depth interviews during pregnancy. Cord blood was collected from the newborns so that their chromosomes could be examined — and in particular, the little caps at their tips known as telomeres.
Telomeres and maternal stress
Telomeres keep our DNA from degrading as our cells divide. They gradually shorten as our cells age and as the result of environmental and health conditions, including stress. Previous work at Boston Children’s has found shortened telomeres in institutionalized children in Romania, as well as children with autism, their mothers and their infant siblings.
It’s important to look at lifetime experiences, not just what happens during pregnancy. As in previous studies, Bosquet Enlow and colleagues found that maternal smoking, higher body mass index and lower socioeconomic status during pregnancy were associated with shorter telomeres in newborns. What’s new is that even newborns whose mothers had experienced stress before pregnancy — specifically sexual abuse in childhood — were more apt to have shortened telomeres.
Also for the first time, the study suggests that positive maternal childhood experiences — familial emotional support — have a protective effect on newborns’ telomeres. Exposures during pregnancy and childhood had an additive impact.
“When looking at the effects of maternal experiences on newborn health, it’s important to look at lifetime experiences, not just what happens during pregnancy,” says Bosquet Enlow.
Male fetuses more vulnerable?
In the final analysis, only maternal smoking in pregnancy and familial emotional support in childhood were significant predictors of newborn telomere length in the overall sample. When boys and girls were considered separately, several other risk factors emerged — but only among boys.
People often study boys and girls together, but there do seem to be sex differences that need to be explored. For boys, lower maternal socioeconomic status, higher body mass index, smoking, depression during pregnancy and sexual abuse of the mother in childhood were associated with shorter telomere length, while a supportive home environment in the mother’s childhood was associated with longer telomeres. None of the examined risk factors had an effect on telomeres in girls.
“People often study boys and girls together, but there do seem to be sex differences that need to be explored,” says Bosquet Enlow. “There is evidence that boys and girls adapt to fetal exposures differently. Male and female fetuses don’t appear to experience the in utero environment in the same way.”
Cautions and questions
Bosquet Enlow and her colleagues continue to track the children’s health and neurodevelopment. They hope to see the study replicated and are also investigating biological mechanisms that might account for telomere shortening in the face of prenatal and childhood risk factors.
How shorter telomeres might affect the children’s future is still an open question.
“It’s still not known what shortened telomeres mean for children’s risk for physical and mental health problems,” says Bosquet Enlow. “Is telomere shortening a cause of health problems? Or is it a marker of biological and environmental exposures that we know increase risk for poorer outcomes in kids?”
The fine print
The paper’s coauthors were Valentina Bollati and Mirjam Hoxha of the Università degli Studi di Milano; Georgios Sideridis of Boston Children’s Hospital; Julie D. Flom of Kravis Children’s Hospital, Icahn School of Medicine at Mount Sinai (New York); and Michele R. Hacker of Beth Israel Deaconess Medical Center. Rosalind J. Wright of the Icahn School of Medicine at Mount Sinai was senior author.
The study was supported by the National Heart, Lung, & Blood Institute (R01HL095606; R01HL114396), the Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01HD082078), the National Institute of Environmental Health Sciences (P30ES023515), and Boston Children’s Hospital’s Clinical and Translational Research Executive Committee and the Program for Behavioral Science in the Department of Psychiatry.