Role of antenatal anxiety in the relationship between maternal exposure to nitrogen dioxide and small for gestational age: A birth cohort study.

Background: Both Nitrogen dioxide (NO ₂ ) exposure and antenatal anxiety have individually been associated with small for gestational age (SGA). Little is known, however, about whether there is effect modification of antenatal anxiety on NO ₂ -related SGA.
Methods: The prospective birth cohort study included 1823 mother-newborn pairs in Guangzhou, China, from January 2017 to April 2020. Exposure to NO ₂ during the pre-conceptional and prenatal periods was estimated using an inverse distance weighted method. Antenatal anxiety was assessed by Trait Anxiety Inventory. SGA was determined by the Chinese gestational age- and sex-specific birthweight standards. Cox proportional hazards regression models was used to estimate hazard ratios (HRs) and 95 % confidence intervals (CIs) for SGA as per 10 μg/m ³ increase in NO ₂ . Modifying effects of trait anxiety on NO ₂ -related SGA were identified by stratified analyses, and three-dimensional response surface plots and two-dimensional heat maps.
Results: Each 10 μg/m ³ increase in NO ₂ exposure during the third trimester was significantly associated with SGA risk among overall participants (HR = 1.221, 95 % CI: 1.014-1.471) and primipara (HR = 1.271, 95 % CI: 1.023-1.579). We found significant effect modification of anxiety level for NO ₂ -related SGA in the third trimester (P _interaction  < 0.05). Pregnant women with higher levels of trait anxiety were more likely to deliver SGA newborns, particularly for those with high trait anxiety (HR = 1.781, 95 % CI: 1.007-2.945). Primiparous women were more susceptible.
Conclusions: This study provides evidence that antenatal trait anxiety may modify the effects of maternal NO ₂ exposure on SGA risk. The third trimester could be a critical window of susceptibility.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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