Hard-Wired in the Womb
Researchers have long understood the critical importance of a fetus’s 40 weeks in utero, and the impact of that development on health. Preterm birth and low birthweight babies—smaller, sicklier babies with immature lungs, brains and nervous systems—often require extensive hospital stays.
Now they are piecing together the complex story of how maternal health, fetal development and the fetal environment set the course for health problems as late as the fifth decade of the child’s life.
This new understanding highlights the need to gain a handle on the social and biological underpinnings of widespread disparity in gestational age and birthweights of babies born around the globe. In the U.S., for example, low-income African-American women experience preterm labor (birth before 37 weeks) at close to twice the rate of white women. That means babies are younger, lighter, sicker.
“We still don’t understand the underlying mechanism,” says family and reproductive health expert Bernard Guyer. Is it social, biological or a combination of both? Some scientists suspect a biological risk factor—it turns out that African-American women, regardless of health economic status and other factors—give birth to smaller babies, at earlier gestational ages. “And if anything, this trend of racial disparity is getting worse,” Guyer says. But answers remain unclear. (See story on race and health disparities, page 37.)
Maternal health expert Donna Strobino and her team are looking into the social, psychosocial and biological risk factors for preterm labor and low birthweight babies. Her work with PhD student Ashley Schempf shows that lifestyle factors and psychosocial risk account for considerable variation in birthweight among low-income women in Baltimore City. She also is looking at the effects of maternal depressive symptoms on the growth of young children.
Researcher Sai Ma is investigating intervention strategies to reduce preterm labor and low birthweight babies. “Some strategies, such as requiring pregnant women to stop smoking or drinking, does show improvement in birthweight,” Ma says. “But the challenge is developing large-scale, population-based intervention strategies.”
These intervention strategies will be critical to leveling the playing field for health outcomes because growing evidence supports the idea of “fetal programming,” which acknowledges that the critical 40 weeks of fetal development affect development of certain diseases later in life including coronary artery disease, type 2 diabetes, hypertension and chronic lung disease. “This whole field of ‘fetal programming’ and life-course development is in its infancy,” notes Guyer.
In the Department of Mental Health, a team of experts including William Eaton has published a series of five studies over the past decade, all showing enhanced risk for babies with obstetric complications. The early studies suggest a “continuum of reproductive casualty” for the range of childhood mental disorders, such as autism, learning disorders, and eating disorders, and adult disorders such as schizophrenia. The continuum hypothesis was first put forth by Hopkins researchers Abraham Lilienfeld, Elizabeth Parkhurst and Benjamin Pasamanick over 50 years ago.
Recent studies suggest, more specifically, that autoimmune diseases in the mother during pregnancy may program the fetal immune system and thereby predispose the infant to autism. A 2009 study, for example, found that children of mothers who have autoimmune diseases such as type 1 diabetes, rheumatoid arthritis and celiac disease have up to a three times greater risk for autism.
Both Eaton and Guyer feel that the life course approach, extending research from conception through death, is crucial to understanding the effects of fetal adversity.
Finding answers will undoubtedly take time, and that’s the challenge. As Eaton notes, “We have studied scores of generations of rodents, and hundreds of generations of fruit flies. But we have yet to study even one generation of human beings completely from conception to death.”