Effects of chemical exposures and diet on birth outcomes in a New York City pregnancy cohort: Mediation through favorable fetal growth conditions.

Background: Fetal growth is shaped by a complex interplay of parental traits, environmental exposures, nutritional intake, and genetic predispositions. In epidemiological research, birth weight is widely used as a proxy of impaired or favorable fetal growth; but it fails to provide a comprehensive measure, particularly if used alone.

Methods: In a cohort of 538 mother-fetal pairs from the New York University Children's Health and Environment Study (NYU CHES), we utilized multiple linear regression and structural equation modeling (SEM) to assess the influence of various determinants-maternal characteristics, chemical exposures, and dietary factors-on fetal growth. To comprehensively evaluate fetal growth, we employed the concept of latent variable Favorable Fetal Growth Conditions (FFGC), together with three observed outcomes: birth weight, birth length, and gestational age.

Results: Maternal characteristics such as height, BMI, race/ethnicity, and maternal alcohol intake were significantly associated with birth weight, birth length, and gestational age in both the linear regression and with FFGC in the SEM. However, SEM additionally revealed significant relationships that were not detected by linear regression. Specifically, di(2-ethylhexyl) phthalate (DEHP) latent factor showed a negative association with the FFGC (β=-0.16, 95% confidence interval (CI)=-0.27, -0.04). The diet latent variable positively impacted FFGC (β=0.15, 95% CI=0.04, 0.25), whereas total calorie intake exhibited a negative effect (β=-0.13, 95% CI=-0.22, -0.05).

Conclusion: The SEM provided a thorough understanding of the multifaceted pathways through which multiple factors of chemical mixtures, diet intakes, and maternal characteristics affected fetal development, uncovering nuanced associations that were not apparent in direct effects models. Our findings highlight the intricate interplay of maternal characteristics, chemical exposures, and dietary factors in shaping fetal growth.