Study first to link maternal chemical exposure with changes in fetal motor activity and heart rate
Researchers at the Johns Hopkins Bloomberg School of Public Health report the first evidence that higher maternal exposure to certain persistent environmental contaminants is associated with measurable differences in fetal behavior. In an exploratory study of 50 pregnant women, higher concentrations of several organochlorine compounds in maternal blood were linked to more frequent and more vigorous fetal motor activity. Some chemical exposures were also associated with fewer fetal heart rate accelerations—changes that normally occur alongside fetal movements and are commonly used as indicators of fetal wellbeing.
Janet A. DiPietro, PhD, lead author and Associate Dean for Research at the Bloomberg School of Public Health, emphasized the importance of measuring fetal neurobehavior directly. “Both fetal motor activity and heart rate reveal how the fetus is maturing and give us a way to evaluate how exposures may be affecting the developing nervous system,” she said. Most studies wait until children are older to assess developmental effects of prenatal exposures; this work detects associations in utero.
The study enrolled 50 pregnant women from higher- and lower-income groups living in and around Baltimore, Maryland. At 36 weeks of pregnancy the researchers collected maternal blood samples and recorded fetal heart rate and motor activity. Blood was analyzed for 11 pesticides and 36 polychlorinated biphenyl (PCB) compounds. Despite bans on many of these substances more than three decades ago, the investigators detected organochlorine compounds in all participants.
Findings were not uniform across all chemicals. When associations with fetal heart rate were observed, higher maternal levels tended to be linked with reductions in fetal heart rate accelerations—an established marker that typically parallels fetal movement and supports assessment of fetal wellbeing. Associations with fetal motor activity were more consistent: higher concentrations of seven out of ten organochlorine compounds were associated with at least one measure indicating more frequent or more vigorous movement. Among the compounds implicated were hexachlorobenzene, DDT, and several PCB congeners. The study also found that women in the higher socioeconomic group had greater concentrations of these persistent contaminants compared with women in the lower socioeconomic group.
These results add to growing concern about the prenatal period as a critical window for brain development. The observed associations suggest that the developing fetus is sensitive to low-level environmental exposures and that fetal neurobehavioral measures can reveal effects before birth. According to the authors, the findings reinforce the need for ongoing efforts to reduce exposure to persistent environmental contaminants that can affect the developing nervous system both prenatally and postnatally.
The study is exploratory and observational, and the authors note several important caveats. The sample size was modest, which limits statistical power and the ability to generalize findings broadly. Observational associations do not prove causation; other unmeasured factors could influence fetal behavior and chemical levels. The measurements reflect exposure late in pregnancy and do not capture exposure timing earlier in gestation. The researchers recommend that future studies with larger, more diverse samples and longitudinal follow-up examine whether these prenatal neurobehavioral associations predict later child development.
Funding and acknowledgements
This research was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) grant 2R01 HD27592 and by the National Institute of Environmental Health Sciences (NIEHS) Center grant ES03819. The study and its authors, including Janet A. DiPietro, Meghan F. Davis, Kathleen A. Costigan, and Dana Boyd Barr, were published in the Journal of Exposure Science and Environmental Epidemiology.
Contact: Tim Parsons, Johns Hopkins University Bloomberg School of Public Health
Source: Johns Hopkins University Bloomberg School of Public Health press release
Image source: Brain gear image credited to NIH (public domain)
Original research: Abstract for “Fetal heart rate and motor activity associations with maternal organochlorine levels: results of an exploratory study,” published online April 17, 2013 in Journal of Exposure Science and Environmental Epidemiology (doi:10.1038/jes.2013.19).