Prenatal exposure to environmental contaminants and cognitive development through 7 y in Mexico
Authors: Casanova Ines Gonzalez , Stein Aryeh D. , DiGirolamo Ann , Barraza‐Villarreal Albino , Rivera Juan , Romieu Isabelle , Feregrino Raquel , Ramakrishnan Usha 
Published: November 2023

Recent evidence suggests that prenatal exposure to environmental contaminants (EC) including indoor and outdoor air pollution, Bisphenol ‐A or pthalates from plastic containers, lead from clay plates and pots, and pesticides can affect cognitive development. The objective of this study was to assess if maternal self‐reported exposure to EC was associated with child development trajectories through 7 y of age.

We used data collected prospectively from 530 children of women participating in a randomized controlled trial of Prenatal Omega‐3 Supplementation on Growth and Development in Mexico, with information available on prenatal exposure to EC and at least two cognitive development measurements between 1 and 7 y. Women completed a prenatal EC between pregnancy weeks 18 to 22. Mothers reported distance from heavy transited streets and industrial areas, types of stoves and fuels used for cooking, personal smoking behavior and exposure to secondhand smoking, cooking and storage behaviors related to plastic and clay use, and exposure to pesticides in home or work. Cognitive development was assessed using the Bayley Scales of Infant Development at 12 and 18 mo, the McCarthy Scales of Children Abilities at 5 y, and the Weschler Abbreviated Scale of Intelligence at 7 y. Composite cognitive raw scores of each test were converted into age‐standardized z‐scores and individual developmental trajectories were assessed using PROC TRAJ in SAS. Multinomial logistic regression was used to test associations between EC and the trajectories. All models were adjusted for socioeconomic status (SES), maternal intelligence (Raven test), stimulation at home (HOME inventory) at 1 y, and child sex and birthweight.

Four distinct trajectories were produced and labeled as 1. Always low scores (AL; 25%) 2. Low to high (LH; 20%), 3. High to low (HL; 26%), and 4. Always high (AH; 29%) (All p<0.001). Only 11% of the mothers reported living near to a highly transited avenue and none reported living near an industrial area. All mothers used gas stoves to cook. 14% smoked before pregnancy and 40% reported a member of the household smoked, but all stopped due to the pregnancy. Only 3% of the women had direct contact with pesticides at home or work during pregnancy. 30% reported using clay pots at least once per week, and 47% used plastic containers to heat food in the microwave at least once per week. Offspring of women who reported using plastic containers to heat their food in the microwave were 83% more likely to belong to the HL trajectory compared to AH (OR [95% CI] =1.83 [1.02 3.32] p<0.05). No other EC was associated with the trajectories. SES was inversely associated with HL (0.68 [0.50 0.92]) and HOME score was inversely associated with AL (0.94 [0.88 0.99]). Maternal intelligence was inversely associated with both AL and HL.

In conclusion, this analysis adds to the evidence that prenatal exposure to EC found in plastic containers may be associated with negative cognitive development outcomes long‐term.

Support or Funding Information

Funded by the Thrasher Research Fund and NIH grants HD043099 and HD058818