Table 3.

Odds ratios (ORs) and 95% confidence intervals (CIs) for the association between exposure to pollutants and fetal heart rate monitoring abnormalities in western Japan, 2005–2010.

	n	No. of outcome	OR per interquartile range increase	95% CI
Exposure during the first trimester
PM a,b
Model 1c	23,782	2,323	1.22	1.07	1.38
Model 2d	23,623	2,303	1.20	1.05	1.37
Ozone
Model 1	23,655	1,975	1.02	0.93	1.11
Model 2	21,628	1,972	1.01	0.92	1.11
NO2 e
Model 1	21,543	2,014	0.83	0.66	1.04
Model 2	21,346	2,000	0.79	0.62	1.01
SO2 f
Model 1	23,477	2,272	1.02	0.91	1.13
Model 2	23,357	2,260	0.98	0.87	1.11
Exposure during the second trimester
PM
Model 1	23,782	2,323	1.12	0.99	1.27
Model 2	23,623	2,303	1.05	0.91	1.21
Ozone
Model 1	23,655	1,975	0.97	0.89	1.07
Model 2	21,628	1,972	0.99	0.90	1.09
NO2
Model 1	21,543	2,014	0.90	0.72	1.13
Model 2	21,346	2,000	1.08	0.83	1.41
SO2
Model 1	23,477	2,272	1.06	0.95	1.18
Model 2	23,357	2,260	1.12	0.97	1.29
Exposure during the third trimester
PM
Model 1	23,623	2,303	1.07	0.97	1.17
Model 2	23,623	2,303	1.06	0.96	1.17
Ozone
Model 1	21,628	1,972	1.07	0.98	1.18
Model 2	21,628	1,972	1.06	0.97	1.17
NO2
Model 1	21,346	2,000	0.86	0.71	1.04
Model 2	21,346	2,000	0.82	0.65	1.02
SO2
Model 1	23,357	2,260	0.98	0.89	1.08
Model 2	23,357	2,260	0.93	0.83	1.05

^aPM = particulate matter.

^bAs an indicator of PM, we used suspended PM, defined as airborne particles with a 100% cut-off level of 10-μm aerodynamic diameter under the Japan Air Quality Standards.

^cAdjusted for maternal age at delivery, birth year, season of conception, parity, smoking during pregnancy, alcohol drinking during pregnancy, gestational age at birth, premature rupture of membranes, mode of delivery, presence of congenital anomalies, and small for gestational age.

^dWe included exposure to pollutant during the first, second, and third trimesters simultaneously.

^eNO₂ = nitrogen dioxide, ^f SO₂ = sulfur dioxide.