In some cases, those epigenetic changes take affect before you’re even born. “A theory in medicine, originally known as the Barker Hypothesis, suggests that the origins of chronic disease, cancer, and mental health begin prenatally and early in the life course,” says Bernard Fuemmeler, PhD, MPH, interim co-leader of the Cancer Prevention and Control program at VCU Massey Cancer Center. Fuemmeler worked on a study that is the first to connect secondhand smoke during pregnancy with epigenetic changes, measured at birth.
The Barker Hypothesis
Fuemmeler explains that the Barker Hypothesis (now referred to as the Developmental Origins of Health and Disease—DOHaD) was named after David Barker, MD, PhD, who, in the 1990s, documented a relationship between birth weight and adult heart disease. “[Barker’s] early findings suggested that what happens during prenatal development appears to matter to our health trajectory as we age,” Fuemmeler says. “What we know now is that there is mounting evidence that prenatal nutrition, environmental exposures to toxins, and even psychological and social stressors, can impact prenatal development and health.” “Maternal smoking during pregnancy has a host of health consequences for the developing baby, including reduced birth weight. Experts believe that exposure to toxins like tobacco smoke during pregnancy alters the epigenetic machinery that supports this rapid developmental period of life,” Fuemmeler states. “These shifts in the epigenetic profile could have consequences [like] later adult disease," Fuemmeler says. “Our study helps to support this hypothesis by examining the epigenetic profile of babies born to non-smoking mothers who varied in their level of secondhand tobacco smoke exposure.”
The Study in Detail
The study, published in Environmental Health Perspectives, looked at data from 79 pregnant women enrolled in the Newborn Epigenetics Study (NEST) between 2005 and 2011. During their first trimester, all women had concentrations of cotinine (a nicotine byproduct) in their blood consistent with low levels of smoke exposure. While some women had almost no cotinine in their blood, others had amounts equal to direct exposure to secondhand smoke.
After the women gave birth, the researchers took blood samples from the umbilical cord. (The umbilical cord carries blood back and forth between the baby and the placenta, supplying nutrients and oxygen to the baby.) They used these samples to carry out what’s known as an epigenome-wide association study (EWAS). Their goal was to look for relationships between blood cotinine levels of the mothers during pregnancy and epigenetic patterns in the babies at birth.
When cotinine levels were higher, the newborns were more likely to have epigenetic “marks” on genes that control the development of brain function, as well as genes related to diabetes and cancer.
Fuemmeler says that before they carried out the research, his team had no idea how much low levels of tobacco smoke exposure—those consistent with secondhand smoke exposure—could change the epigenetic profile of newborns. The findings are clear—no level is safe.
Advice for Moms-to-Be
Sherry Ross, MD, OB/GYN and women’s health expert at Providence Saint John’s Health Center in Santa Monica, California, points out that it’s well known that exposure to secondhand smoke increases the risk of complications to the mom and baby. This includes a greater risk to SIDS and infant breathing problems. “More studies are needed, but this study supports the negative impact of second-hand smoke on the DNA methylation in umbilical cord blood that can cause underlying molecular mechanisms that might cause health issues for a newborn baby,” Dr. Ross says. “These effects may lead to cancer, atherosclerosis, nervous systems disorders, and cardiovascular disease of the newborn.” Ross’s advice to pregnant women is clear. “Avoiding secondhand smoke exposure should be a priority to minimize the health risks to the growing baby,” she says. Meanwhile, Fuemmeler wants policymakers to take action to protect pregnant women and their babies. “The findings draw further attention to the importance of reducing tobacco smoke exposure in our workplaces, homes, and public spaces within our communities, like parks and bus stops,” he says. “We need to think about tobacco-free policies as a form of environmental justice that helps to support those vulnerable who cannot advocate for themselves.”
