Adverse effects of prenatal stress or environmental chemical exposures on foetal growth are well described, yet their combined effect remains unclear. In this study, the authors conducted a systematic review on the combined impact and interaction of prenatal exposure to stress and chemicals on developmental outcomes. The first three steps of the Navigation Guide systematic review were used. A protocol was written, a robust literature search was performed to identify relevant animal and human studies and data was extracted on developmental outcomes. For the most common outcome (foetal growth), the authors evaluated risk of bias, calculated effect sizes for main effects of individual and combined exposures, and performed a random effects meta-analysis of those studies reporting on odds of low birthweight (LBW) by smoking and socioeconomic status (SES). 17 human- and 22 animal-studies of combined chemical and stress exposures and foetal growth were identified. Human studies tended to have a lower risk of bias across nine domains. Generally, stronger effects were found for chemicals than stress, and these exposures were associated with reduced foetal growth in the low-stress group and the association was often greater in high stress groups, with limited evidence of effect modification. Smoking was found to be associated with significantly increased odds of LBW, with a greater effect for high stress (low SES; OR 4.75 (2.46-9.16)) compared to low stress (high SES; OR 1.95 (95% CI 1.53-2.48)). Animal studies generally had a high risk of bias with no significant combined effect or effect modification. The authors concluded that despite concern for the combined effects of environmental chemicals and stress, this is still an under-studied topic, though limited available human studies indicate chemical exposures exert stronger effects than stress, and this effect is generally larger in the presence of stress.
Authors: Vesterinen HM, Morello-Frosch R, Sen S, Zeise L, Woodruff TJ. ; Full Source: PLoS One. 2017 Jul 12;12(7): e0176331. doi: 10.1371/journal.pone.0176331. eCollection 2017.