Superfund Research Program
In Utero PCB Exposures and Infant Development
The continuum of human development that begins with one cell at conception and progresses to a complete human being at birth is characterized by a sequence of precisely orchestrated growth events that serve as the foundation for all subsequent stages of human development. Cell differentiation, organogenesis, and fetal maturation are all apart of this remarkable activity. This dynamic and exacting period of human development in the womb is uniquely vulnerable to chemical insults, including those that originate from maternal environmental pollutant exposures.
In utero exposures to environmental contaminants can occur through maternal-placental transfer. High level maternal exposures to environmental pollutants, such as polychlorinated biphenyls (PCBs), have been associated with congenital anomalies, severe developmental and cognitive impairment, and growth retardation in offspring. Currently, there is concern that intrauterine exposures to low levels of PCBs may be capable of producing subtler behavioral, cognitive and growth effects in newborns and infants that set the stage for impairment in later periods of human development.
Despite ongoing public health concern, there have been few published studies of the health effects of in utero PCB exposures on newborn and infant health outcomes. Moreover, the studies that have been published present conflicting results regarding the effects of low level exposures on infant learning ability, behavior, and growth. Researchers at Harvard University are evaluating the associations between low level in utero PCB exposures and health outcomes in newborns and infants. PCBs are widely occurring environmental contaminants to which the general population is routinely exposed and which also readily cross the placenta.
The health outcomes of interest include infant size, gestational age at birth, infant behavior and neurologic function because these are determinants of perinatal morbidity and mortality, and may be indicators of later childhood and adult neuro-cognitive functioning. This ongoing study is performing two baseline evaluations (at birth and one week of age) and one follow up evaluation (at 6-7 months of age) on a planned cohort of 900 mother-infant pairs. The mothers deliver at St. Luke's Hospital in New Bedford, Massachusetts and live in one of four communities adjacent to the New Bedford harbor Superfund site which is known to be significantly contaminated with PCBs.
Prenatal exposures to PCBs are measured by analysis of cord blood and maternal milk samples. Additional information collected at the baseline evaluations includes neonatal behavioral assessments, infant cry recordings, infant anthropometric assessments (weight, crown-heel length, head circumference), and infant and maternal medical record reviews. A detailed questionnaire is also administered at birth which assesses risk factors for PCB exposures and the developmental outcomes of interest. The follow-up evaluation includes an anthropometric assessment, updated medical and exposure history, home environmental assessment, and administration of the Fagan Test of Infant Intelligence.
Results of preliminary data analyses support the following findings:
- Current population exposures to PCBs may be associated with important impacts on fetal maturation and therefore be a modifiable risk factor for premature births;
- Current low level population exposures to PCBs are unlikely to be associated with major impacts on fetal growth independent of maturation and gestational age (unlike current lead exposures);
- Infant visual memory (assessed by the Fagan Test of Infant Intelligence) may be impaired by in utero PCB exposures in the study population, which is predictive of cognitive performance in later childhood.
Evidence is emerging in both this study and studies by other researchers, which suggests there are associations between low level in utero pollutant exposures and altered developmental achievement and growth in infancy and later childhood. This research is significant for improving the understanding of the growth and developmental consequences of low level in utero exposures to PCBs. Improved understanding of these relationships is key to establishing a rational approach to the prevention of certain developmental disorders in infancy and their long term after effects.
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