Table 2.

Select variables measured during pregnancy and after birth for dyads included in the intention-to-treat analysis of the Ulaanbaatar Gestation and Air Pollution Research trial in Ulaanbaatar, Mongolia, 2014–2019 ($n=475$).

	Control ($n=233$)	Intervention ($n=242$)
	Median (25th, 75th percentile) or $n$ (%)	Median (25th, 75th percentile) or $n$ (%)
Maternal characteristics
Delivery type
Cesarian	86 (37.0)	85 (35.1)
Vaginal	134 (57.5)	151 (62.4)
Unknown [n (%)]	13 (5.6)	6 (2.5)
Blood lead concentration ($\mathrm{\mu }\mathrm{g}/\text{dL}$)	1.46 (1.17, 1.80)	1.43 (1.17, 1.86)
Not measured [n (%)]	61 (26.2)	43 (17.8)
Blood cadmium concentration ($\mathrm{\mu }\mathrm{g}/\text{L}$)	0.22 (0.16, 0.31)	0.19 (0.14, 0.28)
Not measured [n (%)]	61 (26.2)	43 (17.8)
Blood mercury concentration ($\mathrm{\mu }\mathrm{g}/\text{L}$)	0.31 (0.22, 0.54)	0.30 (0.20, 0.44)
Not measured [n (%)]	61 (26.2)	43 (17.8)
WASI Matrix Reasoning raw score	16.0 (12, 19)	17.0 (13, 19)
Not measured [n (%)]	58 (24.9)	33 (13.6)
WASI Vocabulary raw score	36 (32, 39)	35 (31, 39)
Not measured [n (%)]	58 (24.9)	33 (13.6)
Child characteristics
Sex
Female	110 (47.2)	109 (45.0)
Male	112 (48.6)	126 (52.1)
Unknown [n (%)]	11 (4.7)	7 (2.9)
Birth term
Preterm ($<37\mathrm{wk}$)	13 (5.6)	24 (9.9)
Term ($\ge 37\mathrm{wk}$)	207 (88.8)	211 (87.2)
Unknown [n (%)]	13 (5.6)	7 (2.9)
Season of birth
Winter	26 (11.2)	35 (14.5)
Spring	51 (21.9)	56 (23.1)
Summer	69 (29.6)	78 (32.2)
Fall	74 (31.7)	66 (27.3)
Unknown [n (%)]	13 (5.6)	7 (2.9)
Breastfed infant
Never	6 (2.6)	5 (2.1)
$<12\text{\hspace{0.17em}months}$	43 (18.5)	53 (21.9)
$\ge 12\text{\hspace{0.17em}months}$	139 (59.7)	156 (64.5)
Not reported [n (%)]	45 (19.3)	28 (11.8)
HOME inventory total score	30.0 (28.0, 32.5)	30.0 (27.0, 34.0)
Not measured [n (%)]	76 (32.6)	77 (31.8)
Blood lead concentration at 2 y of age (ug/dL)	2.60 (1.86, 3.63)	2.47 (1.68, 3.47)
Not measured [n (%)]	80 (34.3)	68 (28.1)
Blood cadmium concentration at 2 y of age ($\mathrm{\mu }\mathrm{g}/\text{L}$)	0.05 (0.04, 0.08)	0.05 (0.04, 0.08)
Not measured [n (%)]	80 (34.3)	68 (28.1)
Blood mercury concentration at 2 y of age ($\mathrm{\mu }\mathrm{g}/\text{L}$)	0.18 (0.13, 0.25)	0.18 (0.13, 0.27)
Not measured [n (%)]	80 (34.3)	68 (28.1)
Child’s age at WPPSI-IV assessment (months)	48.0 (48, 48)	48.0 (48, 48)
No WPPSI-IV [n (%)]	51 (21.9)	40 (16.5)
HEPA filter air cleaner usage after birth
Yes	39 (16.8)	33 (13.6)
No	133 (57.0)	162 (66.9)
Not reported [n (%)]	61 (26.2)	47 (19.4)

Note: Percentages may not total 100 due to rounding. HEPA, high-efficiency particulate air; HOME, Home Observation Measurement of the Environment; WASI, Wechsler Abbreviated Scale of Intelligence; Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition.