A pregnant woman has a laundry list of things to avoid for the sake of her baby’s health: alcohol, raw fish, smoking and more.
But what about things that aren’t so tangible or easy to identify and avoid?
A growing body of evidence shows that maternal trauma can also impact a child’s health. University of Florida Emerging Pathogens Institute member Connie Mulligan, Ph.D., a professor at the UF College of Liberal Arts and Sciences Anthropology Department, studies how violence and stress in mothers in the Democratic Republic of the Congo (DRC) affect their newborn’s health.
In this ongoing work, she has already found that mothers who have experienced psychosocial stress are more likely to have infants with lower birthweights and a less diverse gut microbiome — two conditions that come with a higher risk of disease, inhibited cognitive development and fetal mortality.
Mulligan, also a member of the UF Genetics Institute, began this research out of interest in how genetic and non-genetic factors work together to affect mental and physical health.
“Most people stay in their lane,” she said. Geneticists tend to focus on DNA, while epidemiologists and cultural anthropologists examine information like patterns of disease, cultural dissonance and demographics.
Such siloes keep research simple but can be a disservice to real-life communities where complex interactions do exist. A genetic variant, for example, may influence how someone reacts to a traumatic event.
“It’s very important that we know someone’s genetic background in addition to their stressful and traumatic experiences, so we can test for interactions,” Mulligan said.
Members of the scientific community generally accept the idea that stress can have physical symptoms. Nevertheless, the notion that this effect can also be intergenerational – that a mother’s stress can impact her baby’s health, possibly into adulthood – has less support, mainly because it is under-researched.
Since 2010, Mulligan’s team of researchers has been working in the DRC to better understand the issue. They have enrolled several cohorts of mothers and babies in collaboration with the HEAL Africa Hospital, which was established to help the local people cope with the physical and psychological effects of war.
The researchers gather measurements such as the newborns’ birthweight and the mothers’ weight and age. They also collect blood samples from the mother and child, and several infant stool samples over periodic follow-up visits.
A separate team, trained to interview victims of violence, asked the mothers about their experiences with general trauma, sexual trauma, war trauma and chronic stress.
“It’s a very different type of data to collect compared to genetic data,” Mulligan said. “I was fascinated by this idea. How do you measure the stressful and traumatic experiences that are so impactful on our mental and physical health?”
Collecting that information can also be fraught, since a common human response after trauma is to downplay or even deny what happened as a defense mechanism. Different people may have varied accounts and responses to the same traumatic event. Mulligan likens it to trying to catch smoke.
The next hurdle: deciding how to measure health outcomes. This is an eternal quest for Mulligan’s team, but so far they have found birthweight and the gut microbiome to be good proxies for an infant’s overall well-being.
“[Birthweight and the gut microbiome] give us a broad look at a person’s health, not just across many different diseases, but throughout the lifespan,” Mulligan said.
Technological advancements also make gathering data on the gut microbiome easier than ever. In a recent paper showing that infants of high-stress mothers have reduced levels of healthy bacteria, Mulligan and collaborators studied the infant gut microbiome in the context of maternal stress down to the species and sub-species level for the first time.
“You want to be able to say which species of bacteria a person is deficient in and, therefore, would benefit from a probiotic with that bacterial species in it,” Mulligan explained. In this case, it would be Lactobacillus gasseri and Bifidobacterium pseudocatenulatum.
Although researchers aren’t sure precisely what mechanism makes it possible for a mother’s psychosocial stress to alter her baby’s health outcome, Mulligan suspects the answer may lie in DNA methylation.
In this natural biological process, a methyl group — containing one carbon atom and three hydrogen atoms — gets tacked onto a DNA strand. The function of that DNA segment is then changed, even though its sequence is unaltered.
DNA methylation is the body’s way of turning various genes on and off. It plays a vital role in processes like embryo formation and aging, but it can be dangerous if it makes a mistake like silencing a tumor suppression gene.
Our genome, which contains our entire DNA sequence, doesn’t change in response to stress. But the epigenome, made up of chemical processes like DNA methylation that modify the genome, is fluid throughout life.
Mulligan suspects humans may have evolved a subset of genes that interact with the epigenome, allowing our bodies to be responsive to environmental and psychosocial stressors. Meanwhile, other genes would remain untouched.
“Are there some DNA methylation marks that are made early in life in response to stress?” Mulligan wondered. “And similarly, can the microbiome be changed in a way?”
Both are moldable and, if inherited, could have cascading implications for the health of the mother and child. Understanding the potential role of DNA methylation and the infant gut microbiome will be key to mitigating the issue since simply reducing stress and trauma is no small feat.
Humanitarian agency UNICEF has noted high levels of sexual violence in the DRC. Mulligan’s team saw this reality reflected in the mothers’ answers to their questions.
Sexual prevalence is also disturbingly common in the United States, where one in four women have experienced rape.
“Even though my research site is halfway around the world, everything we learn there is applicable to the U.S., because we do have horrific levels of sexual violence, whether we want to admit it or not,” Mulligan said. “We also have high levels of poverty and discrimination. These are all different stressors and trauma that impact our mental and physical health.”
Despite the significant trauma and hardship mothers in the study cohorts have experienced, Mulligan said they are also some of the most joyful people she has met.
“They’re like moms here in the U.S.,” she said. “They want to know what they can do to improve their kids’ lives when they’re dealing with what life has thrown at them.”
She added that scientists have a tendency to focus on negative outcomes and may miss out on more positive measures like resilience and coping mechanisms. With more grant funding, Mulligan hopes to remedy this in the future.
The team also plans to expand the project to examine how the gut microbiome, itself inflamed by maternal stress, may affect infants’ susceptibility to malaria. What they learn may also be relevant to other infectious diseases.
While the work continues, Mulligan said the research already has one clear lesson: when people experience extreme stress and trauma, we as a society should do something to help.
Written by: Jiayu Liang