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The Fetal Origins of Obesity

March 02, 2015
by Michael Greenwood

A new member of the YSPH faculty is seeking to understand how the seeds of obesity are planted before birth.

Nicola Hawley, an assistant professor in the Department of Chronic Disease Epidemiology, specializes in maternal and child health and how it is affected by obesity and diabetes, especially in developing countries. Much of her work has been done in American Samoa and other areas of the South Pacific, where she is looking at the factors that lead to widespread obesity. Longer term, she wants to develop a fuller understanding the fetal origins of obesity and develop effective interventions for both mother and child. Hawley joined the Yale School of Public Health in 2014.

Genes and environment factors are known to play a role in the development of obesity. Can a fetus exposed to certain factors, such as the mother’s diet and lifestyle, increase their chances of becoming obese as well?

NH: Yes. There is a growing body of evidence that shows that exposures during pregnancy, dietary or environmental, can have a long-lasting effect on our health in childhood and that effect can be sustained into adulthood. In fact, we now believe that the time we spend in the womb, or in utero, may be the most critical period of life for the development of a number of adult diseases - obesity, diabetes, and hypertension included. There has been a real shift in obesity research from thinking about energy in-energy out at a particular moment in time to a greater focus on multiple exposures across the whole life course.

What are some of the exposures, in particular, that might promote obesity after birth?

NH: There have been a number of prenatal exposures associated with infant or child obesity. These are wide-ranging, from maternal nutritional status, to the type of chemicals the mother is exposed to during pregnancy, to whether she smokes, drinks alcohol or caffeine, takes antibiotics during pregnancy or the type of delivery she has. My own research is focused on maternal nutritional status – mother’s weight at conception, her weight gain during pregnancy, and whether or not she develops diabetes during pregnancy. For a lot of these exposures we still have work to do to understand the underlying mechanisms by which obesity risk is transmitted to her child.

In addition to obesity, are there other health risks that these newborns might face?

NH: Infants born to mothers who are obese when they conceive, gain excess weight during pregnancy or develop gestational diabetes are at risk of pre-term birth, congenital abnormalities, being born large (which necessitates a cesarean delivery, which carries its own risks for mom and baby) or stillbirth.

It sounds as if much of this could be prevented by lifestyle and dietary changes in the mother-to-be.

NH: The time when a woman is pregnant is a fantastic opportunity for intervention to lower obesity risk in her child. Mothers tend to be concerned about the health of their baby during pregnancy and may be willing to change behaviors for the baby’s benefit. It’s also a time where most women are in very frequent contact with their healthcare providers so they can receive education and support for their behavior change.

Are there coordinated interventions in the area already underway?

NH: A number of interventions have focused on limiting gestational weight gain, changing diet and activity patterns during pregnancy or preventing gestational diabetes. Few have focused on lowering pre-conception weight.

How successful have they been?

NH: The gestational weight gain trials have had varying success. Sadly, these interventions seem to be most effective in normal weight, higher income women. Overweight and obese women, ethnic minorities, and lower-income women have a much harder time staying within the weight gain guidelines set by the Institute of Medicine even when they receive intensive intervention. We still have some work to do to understand how we can improve interventions that target these groups.

Is this a relatively new area of research?

NH: This is an area of research that has been growing since the early 1990s when a British scientist first coined the term “fetal origins hypothesis” to explain the link between birth weight and coronary heart disease. There has been enormous progress in this area recently because of advances in epigenetics and technologies like ultrasound which allow us to explore the mechanisms behind the associations we see.

How serious an issue is childhood obesity in America?

NH: Childhood obesity is a huge public health concern. Children who are obese tend to become obese adolescents and adults, and with that there are high personal and societal costs. Some recent reports suggest that childhood obesity is leveling off in the US, but I would encourage people to look beyond the total prevalence figures, at some of the disparities among ethnic groups – while there have been successes in some groups, the rise in obesity is striking among others.

What are your long-term research goals?

NH: My long term goals are to contribute to a greater mechanistic understanding of the fetal origins of obesity, and to apply epidemiological data to the design and implementation of interventions targeted at pregnant women and infants to try and break the intergenerational obesity cycle. I’d like to find ways to integrate these interventions into existing primary care practice.

How did you become interested in this field?

NH: As I was a graduate student, the fetal origins of health and disease literature was just starting to become prominent among the scientific community and getting some media attention – I was fascinated and was lucky enough to be able to find collaborations to help me explore this topic.

You did research on American Samoa. How important was this experience?

NH: My work in American Samoa has been incredibly important. The American Samoans have the highest burden of obesity in the world and in that sense may be a forecast for what some other developing countries will experience in the future. We can learn a lot about how to intervene in cases of extreme obesity from the American Samoan population. They are also genuinely warm and welcoming people and I feel strongly about giving back to the community and developing interventions that can be implemented there with very limited healthcare resources.

What is your most surprising research finding so far?

NH: Finding that 35 percent of American Samoan infants are overweight or obese by 15 months of age was a big surprise (that’s more than double the prevalence in the general US population). It made me committed to understanding why and finding ways to intervene.

What did you do before joining the Yale School of Public Health?

NH: Before coming to Yale I spent five years at Brown, first in the International Health Institute where my Samoan research began, and then at the Weight Control and Diabetes Research Center where I learned about the implementation of obesity interventions from some of the best in the field.

When free time allows, what are some of the activities that you like to pursue?

NH: I was a college volleyball player so you might find me playing recreationally or supporting the Yale team. I love to travel and try and see a new city or a new country every year. This year I have set myself a challenge to read the 52 books recommended by TED speakers, we’ll see how that goes …

To learn more about Nicola Hawley’s work and research interests, visit her faculty page at

Submitted by Denise Meyer on March 03, 2015