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Table 4 Interaction of covariates and PM2.5 exposure during first trimester with the risk of HDP

From: Correlation between exposure to fine particulate matter and hypertensive disorders of pregnancy in Shanghai, China

Covariates Multiplicative scale Additive scale
RR (95% CI) RERI (95% CI)a
Maternal age (≥ 35 years) 0.61 (0.33–1.15) 0.32 (− 0.18–0.81)
Parity (Nulliparous) 2.28 (1.28–4.06) 0.92 (0.46–1.38)
Parental history of chronical diseases (Yes) 1.04 (0.69–1.55) 0.20 (− 1.22–1.62)
Season of conception (Spring or winter) 0.89 (0.31–1.92) −0.09 (− 1.62–1.44)
Pre-conception BMI (Underweight) 2.03 (0.93–4.46) 0.42 (− 0.10–0.93)
Pre-conception BMI (Overweight or obesity) 1.24 (0.81–1.87) 0.26 (−0.47–0.99)
  1. aRERI = 0: indicates no interaction. RERI < 0: indicates negative interaction or less than additive interaction. RERI > 0: indicates positive interaction or more than additive interaction