Maternal Secondhand Smoke Exposure Enhances Macrosomia Risk Among Pregnant Women Exposed to PM2.5: A New Interaction of Two Air Pollutants in a Nationwide Cohort

Abstract

Background: Fine particulate matter (PM2.5) is one of the most common outdoor air pollutants, and secondhand smoking (SHS) is an important source of inhalable indoor air pollution. Previous studies were controversial and inconsistent about PM2.5 and SHS air pollutants on neonatal birth weight outcomes, and no studies assessed the potential interactive effects between PM2.5 and SHS on birth weight outcomes.Purpose: To investigate the interaction between gestational PM2.5 and SHS air pollution exposure on the risk of macrosomia among pregnant women and examine the modifying effect of SHS exposure on the association of PM2.5 air pollution and birth weight outcomes during pregnancy.Methods: Research data were derived from the National Free Preconception Health Examination Project (NFPHEP), which lasted 3 years from January 1, 2010, to December 31, 2012. At least 240,000 Chinese women from 220 counties were enrolled in this project. PM2.5 exposure concentration was obtained using a hindcast model specific for historical PM2.5 estimation from satellite-retrieved aerosol optic depth. Different interaction models about air pollution exposure on birth weight outcomes were established, according to the adjustment of different confounding factors and different pregnancy stages. The establishment of interaction models was based on multivariable logistic regression, and the main confounding factors were maternal age at delivery and pre-pregnancy body mass index (BMI) of participants. SHS subgroups analysis was conducted to further confirm the results of interaction models.Results: In total, 197,877 participants were included in our study. In the full-adjusted interaction model, maternal exposure to PM2.5 was associated with an increased risk of macrosomia in whole, the first-, second-, and third trimesters of pregnancy (p < 0.001). The interactive effect was statistically significant between maternal exposure to PM2.5 and SHS on the risk of macrosomia in the whole (interaction p < 0.050) and the first-trimester pregnancy (interaction p < 0.050), not in the second (interaction p > 0.050) or third trimester (interaction p > 0.050) of pregnancy. The higher frequency of SHS exposure prompted the stronger interaction between the two air pollutants in the whole pregnancy and the first-trimester pregnancy.Conclusions: In the whole and first-trimester pregnancy, maternal exposure to SHS during pregnancy enhanced the risk of macrosomia among pregnant women exposed to PM2.5 air pollutants, and the interaction became stronger with the higher frequency of SHS exposure.

Interaction of PM2.5 and pre-pregnancy body mass index on birth weight: A nationwide prospective cohort study

“…Unadjusted and adjusted linear regressions were used to evaluate the associations between trimester-specific PM 2.5 concentrations and neonatal birthweight as well as the association between pre-pregnancy BMI and birthweight. The confounding factors for adjustment included maternal age at delivery, neonatal sex (male, female), smoking or alcohol intake during pregnancy (still, quit, never), gestational week, maternal educational level (junior high school, senior high school, college), prolonged pregnancy (yes, no), multiparity (yes, no), pre-pregnancy diabetes mellitus (yes, no), and pre-pregnancy hypertension (yes, no) ( 17 , 18 ). The dose-response relationships between PM 2.5 concentration and birthweight were further investigated using restricted cubic spline models (node was 4).…”

“…As for the environmental factors, adverse impacts of PM 2.5 on public health have been huge concerns worldwide, especially in developing countries. However, studies on the adverse effects of gestational PM 2.5 exposure on birthweight can be controversial and inconsistent ( 17 , 18 ). Majority of studies demonstrated correlations between PM 2.5 and low birthweight or small for gestational age (SGA) ( 19 – 25 ), while some studies confirmed associations between PM2.5 and LGA or macrosomia ( 10 , 17 , 18 , 26 ).…”

“…However, studies on the adverse effects of gestational PM 2.5 exposure on birthweight can be controversial and inconsistent ( 17 , 18 ). Majority of studies demonstrated correlations between PM 2.5 and low birthweight or small for gestational age (SGA) ( 19 – 25 ), while some studies confirmed associations between PM2.5 and LGA or macrosomia ( 10 , 17 , 18 , 26 ). Previous studies pointed out that marked differences on PM 2.5 pollution between rapidly developing and developed countries might cause inconsistency in results ( 17 , 18 ).…”

“…Majority of studies demonstrated correlations between PM 2.5 and low birthweight or small for gestational age (SGA) ( 19 – 25 ), while some studies confirmed associations between PM2.5 and LGA or macrosomia ( 10 , 17 , 18 , 26 ). Previous studies pointed out that marked differences on PM 2.5 pollution between rapidly developing and developed countries might cause inconsistency in results ( 17 , 18 ). Air pollution was an extremely serious issue of China during 2010s, when many provinces and cities had annual average PM2.5 over 80 μg/m 3 ( 18 ).…”