Table 4 Adjusted ORs (95% CI) for PROM and PPROM associated with 10 μg/m³ Increase in PM2.5 and with quartiles of PM2.5 (relative to the lowest quartile) in the last week and last day of pregnancy (N = 4364)^a

 PM2.5 (10 μg/m³)

1.01 (0.97, 1.04)

1.04 (0.96, 1.12)

 < 37.5

1.0

1.0

 37.5 to < 75

0.79 (0.60, 1.05)

1.01 (0.55, 1.85)

 75 to < 112.5

0.84 (0.63, 1.11)

0.83 (0.43, 1.59)

 ≥112.5

1.00 (0.74, 1.34)

1.36 (0.71, 2.61)

 PM2.5 (10 μg/m³)

1.02 (1.00, 1.05)

1.04 (0.99, 1.10)

 < 59

1.0

1.0

 59 to < 118

0.99 (0.75, 1.30)

0.95 (0.52, 1.74)

 118 to < 177

0.90 (0.68, 1.20)

0.96 (0.51, 1.78)

 ≥177

1.28 (0.96, 1.69)

1.44 (0.78, 2.66)