January 20, 2020Neonatology
Persistent organic pollutants (POPs) are chemicals once used in agriculture, disease control, manufacturing, and industrial processes. They include the pesticide DDT and dioxin, a byproduct of herbicide production and paper bleaching. POPs are slow to break down, may persist in water and air, and may be passed through the food chain. Their health effects vary, but some compounds have been linked to reproductive disorders and a higher risk of birth defects. Earlier studies of the potential effects of POP exposure during pregnancy have produced conflicting results. According to the authors, most of these studies looked at infant birth weight and length, measures that could suggest impaired fetal growth but could also indicate genetic factors that lead to smaller birth size and weight. Moreover, previous studies have investigated POPs as individual chemicals, but people typically are exposed to a mix of these compounds.
According to an article published in JAMA Pediatrics (30 Dec 2019), POPs in maternal blood have been linked to smaller fetal size, suggesting that chemicals which are no longer produced in the United States but persist in the environment, may have lasting health effects even at low levels. Study results showed that, according to an analysis of ultrasound scans, pregnant women exposed to POPs had slightly smaller fetuses than women who haven't been exposed to these chemicals,. The authors also found that the women in their study had lower levels of POPs than women in the 2003-2004 U.S. Health and Nutrition Survey, the most recent comprehensive study of these compounds in U.S. pregnant women.
In the current study, the autors analyzed records, stored blood samples, and a series of ultrasound scans taken from weeks 16-40 of 2,284 pregnant women enrolled in the NICHD Fetal Growth Study from 2009 to 2013. The blood samples were tested for the presence of 76 POPs soon after the women began the study. The POP levels in each woman's blood were listed as percentiles, with the highest levels set at 100 and the lowest at 1. The authors then compared growth measurements of head circumference, abdominal circumference, and femur (thigh bone) length of the fetuses of women in the 75th percentile to those of women in the 25th percentile. Results showed that, compared to fetuses in the 25th percentile of exposure to organochlorine pesticides, the fetuses of women with exposure in the 75th percentile had the most widespread growth reductions, with head circumference reduced by an average of 4.7 mm, abdominal circumference reduced by 3.5 mm, and femur length reduced by 0.6 mm. High levels of dioxin-like polychlorinated biphenyls were associated with an average head circumference reduction of 6.4 mm and an abdominal circumference reduction of 2.4 mm. High levels of polybrominated diphenyl ethers -- flame-retardant chemicals used in furniture, electronics and other consumer products -- were associated with an average abdominal circumference reduction of 2.4 mm and an average femur length reduction of 0.5 mm.