Table 1.

Maternal and infant demographics by gestational age.

Total $N=\mathrm{174,186}$	$<37\mathrm{wk}$ ($n=\mathrm{15,134}$)	$\ge 37\mathrm{wk}$ ($n=\mathrm{159,052}$)
Gestational age, mean weeks (SD), $\text{missing}=0$	34.5 (2.8)	39.7 (1.4)
Birth weight, mean grams (SD), $\text{missing}=6$	2,598 (752)	3,348 (444)
Parity, mean children (SD), $\text{missing}=0$	2.3 (2.3)	2.1 (2.4)
Quintile of nSES Index,a mean (SD), $\text{missing}=0$	1.9 (1.3)	2.2 (1.4)
Infant sex [$n$ (%)]
Male	8,282 (54.7)	80,774 (50.8)
Female	6,850 (45.3)	78,278 (49.2)
Missing ($n$)	2	0
Maternal age [$n$ (%)]
$<20$	1,322 (8.7)	11,658 (7.3)
20–24	2,980 (19.7)	30,731 (19.3)
25–29	3,440 (22.7)	38,339 (24.1)
30–34	3,702 (24.5)	43,372 (27.3)
$35+$	3,690 (24.4)	34,952 (22.0)
Missing ($n$)	1	2
Maternal Race [$n$ (%)]
White	1,842 (12.2)	29,749 (18.7)
Black	3,027 (20.0)	22,487 (14.1)
Hispanic	8,997 (59.5)	89,592 (56.3)
Asian	916 (6.1)	13,670 (8.6)
Others	352 (2.3)	3,554 (2.2)
Missing ($n$)	216	2,526
Maternal education [$n$ (%)]
High school graduate or less	8,909 (58.9)	81,542 (51.3)
Some college to bachelor’s degree	4,928 (32.6)	57,883 (36.4)
More than a bachelor’s degree	1,297 (8.6)	19,627 (12.3)
Missing ($n$)	435	4,584
Maternal nativity [$n$ (%)]
U.S.-born	10,802 (71.4)	111,087 (70.0)
Foreign-born	4,332 (28.6)	47,965 (30.2)
LUR modeled ${\mathrm{NO}}_2$ exposure, mean ppb (SD), $\text{missing}=0$	23.8 (2.6)	23.6 (2.7)
High noise at residence [$n$ (%)]
$\ge 65\text{dB}$ CNEL	779 (5.2)	6,685 (4.2)
$<65\text{dB}$ CNEL	14,355 (94.8)	152,367 (95.8)
Cigarette smoking [$n$ (%)]
Ever during pregnancy	157 (1.0)	923 (0.6)
Never during pregnancy	14,977 (99.0)	158,129 (99.4)
Missing	1,686	11,681

Note: Data are complete unless otherwise indicated. CNEL, community noise equivalent level; dB, decibels; LUR, land use regression.

^anSES measured as a composite index of seven indicator variables based on U.S. census data at the census tract level.