Table 1.

Select baseline variables for participants included in the intention-to-treat analysis of the Ulaanbaatar Gestation and Air Pollution Research trial in Ulaanbaatar, Mongolia, 2014–2015 ($n=475$).

	Control ($n=233$)	Intervention ($n=242$)
	Median (25th, 75th percentile) or $n$ (%)	Median (25th, 75th percentile) or $n$ (%)
Maternal age at enrollment	28 (25, 32)	29 (25, 33)
Not reported [n (%)]	6 (2.6)	6 (2.5)
Weeks pregnant at enrollment	11 (9, 13)	11 (8, 13)
Not reported [n (%)]	8 (3.4)	12 (4.9)
Enrollment season
Winter	76 (32.6)	72 (29.8)
Spring	73 (31.3)	65 (26.7)
Summer	24 (10.3)	31 (12.8)
Fall	60 (25.8)	74 (30.6)
Marital status
Married or common law	183 (78.5)	209 (86.4)
Not married or common law	49 (21.0)	33 (13.6)
Not reported [n (%)]	1 (0.4)	0 (0.0)
Lived with a smoker at enrollment
Yes	117 (50.2)	119 (49.2)
No	111 (47.6)	119 (49.2)
Not reported [n (%)]	5 (2.2)	4 (1.7)
Maternal education
Completed university	187 (80.3)	193 (79.8)
Did not complete university	31 (13.3)	29 (12.0)
Not reported [n (%)]	15 (6.4)	20 (8.3)
Monthly household incomea
$\ge \mathrm{800,000}$ Tugrik	182 (78.1)	191 (78.9)
$<\mathrm{800,000}$ Tugrik	46 (19.7)	47 (19.4)
Not reported [n (%)]	5 (2.2)	4 (1.7)
Parity
0	73 (31.3)	79 (32.6)
1	92 (39.5)	88 (36.4)
$\ge 2$	51 (22.0)	62 (25.6)
Not reported [n (%)]	17 (7.3)	13 (5.4)

Note: Percentages may not total 100 due to rounding.

^a At the time of data collection 800,000 tugriks was equivalent to approximately $\$360\text{\hspace{0.17em}USD}$.