3.6 Principal component analysis of pollutants during pregnancy
In the WQS model, O3 during pregnancy was found to play an important role in the onset of eczema before two years of age, so we conducted a Principal Component Analysis of the pollutants during pregnancy, with a cumulative contribution of 93.2% from PC1 and PC2 (Figure 6), the largest coefficient component in PC1 was O3 (0.838), and the largest coefficient component in PC2 was PM2.5-10 (0.718). Including PC1 and PC2 in the logistic regression model, PC1 was positively associated with the risk of cumulative eczema (aOR 1.011, 95% CI 1.007-1.015) (Table 6).