Table 3.

Summary of meta-analysis of studies on air pollutant exposures and hypertensive disorder of pregnancy.

Pollutant and exposure window combination	Studies included	Total number of cases	Heterogeneity p-value	Summary OR (95% CI)
Outcome: Preeclampsia
NO2				per 10 ppb
Full gestational period	1, 6, 8, 10, 11	3629	0.71	1.10 (1.03-1.17)
Trimester 1	1, 6, 10, 11	3488	0.79	1.03(0.97-1.10)
Trimester 2	1, 6, 10, 11	3488	0.67	1.05(0.98-1.12)
PM10				per 10 μg/m3
Full gestational period	1, 8, 10, 11	2686	0.55	0.98(0.91-1.05)
Trimester 1	1, 3, 10, 11	3686	0.66	0.99(0.92-1.07)
PM2.5				per 5 μg/m3
Trimester 1	1, 3, 10, 11	2822	0.15	1.10(0.96,1.26)
Outcome: Hypertensive disorder of pregnancy (includes gestational hypertension and preeclampsia)
CO				per 1 ppm
Full gestational period	10, 11, 12, 13	5576	<0.001	0.86(0.53-1.41)
Trimester 1	4, 10, 11, 12	3615	0.12	1.79(1.31-2.45)
Trimester 2	4, 10, 11, 12	3615	0.29	1.22(0.90-1.64)
NO2				per 10 ppb
Full gestational period	1, 6, 7, 8, 10, 11, 12	4916	0.047	1.16(1.03-1.30)
Trimester 1	1, 6, 7, 10, 11, 12b	4775	0.029	1.16(1.02-1.31)
Trimester 2	1, 6, 8, 10, 11, 12c	4666	0.031	1.15(1.02-1.30)
Trimester 1	1, 4, 6, 10, 11, 12	4661	0.42	1.05(0.99-1.12)
Trimester 2	1, 4, 6, 10, 11, 12	4661	0.39	1.03(0.96-1.11)
O3				per 10 ppb
Trimester 1	2, 3, 4, 5, 10, 11, 12	10038	0.81	1.09(1.05-1.13)
	2, 4, 5, 10, 11, 12d	8897	0.71	1.09(1.04-1.14)
	3, 4, 5, 10, 11, 12e	7960	0.73	1.09(1.04-1.15)
Trimester 2	4,10,11,12	3615	0.006	1.12(0.90-1.39)
PM10				per 10 μg/m3
Full gestational period	1, 7, 8, 9, 10, 11	15021	0.001	1.10(0.96-1.26)
	1, 7, 9, 10, 11b	14880	0.001	1.09(0.94-1.25)
	1, 8, 9, 10, 11c	14771	0.004	1.06(0.93-1.20)
Trimester 1	1, 2, 3, 4, 10, 11	5900	0.58	1.02(0.95-1.08)
	1, 2, 4, 10, 11d	4759	0.44	1.02(0.95-1.09)
	1, 3, 4, 10, 11e	3822	0.84	0.99(0.92-1.06)
Trimester 2	1, 4, 10, 11	2681	0.85	0.97(0.89-1.05)
PM2.5				per 5 μg/m3
Full gestational period	1, 9, 10, 11, 12	15245	<0.001	1.15(0.94-1.40)
Trimester 1	1, 2, 3, 4, 10, 11, 12	5207	0.01	1.18(0.98-1.41)
	1, 2, 4, 10, 11, 12d	4508	0.007	1.18(0.94-1.48)
	1, 3, 4, 10, 11, 12e	3995	0.007	1.20(0.93-1.54)
Trimester 2	1, 4, 10, 11, 12	3296	<0.001	1.17(0.79-1.75)

^aReferences are as follows: 1, Dadvand et al. 2013; 2, Lee et al. 2013 (Gestational Hypertension); 3, Lee et al. 2013 (Preeclampsia); 4, Mobasher et al. 2013; 5, Olsson et al. 2013; 6, Pereira et al. 2013; 7, van den Hooven et al. 2011 (Gestational Hypertension); 8, van den Hooven et al. 2011 (Preeclampsia); 9, Vinikoor-Imler et al. 2012; 10, Wu et al. 2011 (Los Angeles); 11, Wu et al. 2011 (Orange County); 12, Xu et al. 2013; 13, Zhai et al. 2012.

^bSensitivity analysis excluding van den Hooven et al. 2011 (Preeclampsia).

^cSensitivity analysis excluding van den Hooven et al. 2011 (Gestational Hypertension).

^dSensitivity analysis excluding Lee et al. 2013 (Preeclampsia).

^eSensitivity analysis excluding Lee et al. 2013 (Gestational Hypertension).