Table 1.

Characteristics of the study population among selected ECHO cohorts ($N=\mathrm{3,339}$).

Characteristic	$N$ (%) or $\text{mean}\pm \text{SD}$
Maternal race/ethnicity
Hispanic/Latina	653 (20.8)
Non-Hispanic White	1,687 (53.8)
Non-Hispanic Black	509 (16.2)
Non-Hispanic Asian	193 (6.2)
Non-Hispanic other	96 (3.1)
Unknown	201
Maternal educational attainment
$<\text{High\hspace{0.17em}school}$	312 (9.5)
High school degree, GED, or equivalent	530 (16.1)
Some college, no degree	702 (21.4)
Bachelor’s degree and above	1,742 (53.0)
Unknown	53
Maternal age at delivery (y)
$<25$	497 (15.7)
25–29	672 (21.3)
30–34	1,124 (35.6)
$\ge 35$	867 (27.4)
Unknown	179
PSS scale
PSS t-score category	$49.8\pm 9.9$ a
$<\text{Median}$ (50.6)	1,003 (49.9)
$\ge \text{Median}$ (50.6)	1,006 (50.1)
Unknown	1,330
Gestational age (wk)	$38.9\pm 1.9$
Preterm birth ($<37$ wk)
Yes	252 (7.5)
No	3,087 (92.5)
Birthweight (g)	$\mathrm{3,337.4}\pm 563.3$
Low birthweight ($<\mathrm{2,500}\mathrm{g}$)
Yes	182 (5.5)
No	3,157 (94.5)
Size for gestational ageb
Small-for-gestational-age	357 (10.7)
Appropriate-for-gestational-age	2,623 (78.6)
Large-for-gestational-age	359 (10.8)
Child sex
Male	1,643 (49.2)
Female	1,696 (50.8)
Parity prior to indexed birth
0	1,783 (53.4)
$\ge 1$	1,556 (46.6)
Prenatal tobacco use
Yes	200 (7.2)
No	2,573 (92.8)
Unknown	165
Prenatal secondhand smoke
Yes	1,386 (64.0)
No	781 (36.0)
Unknown	1,172
Prepregnancy BMI (${\mathrm{kg}/\mathrm{m}}^2$)	$26.1\pm 6.3$ c
Gestational diabetes
Yes	321 (10.5)
No	2,722 (89.5)
Unknown	296
Gestational hypertension
Yes	154 (8.5)
No	1,667 (91.5)
Unknown	1,518
Preeclampsia
Yes	104 (5.6)
No	1,751 (94.4)
Unknown	1,484
Year of birth
1999	28 (0.8)
2000	330 (9.9)
2001	310 (9.3)
2002	170 (5.1)
2003	4 (0.1)
2009	9 (0.3)
2010	122 (3.7)
2011	225 (6.7)
2012	283 (8.5)
2013	243 (7.3)
2014	204 (6.1)
2015	278 (8.3)
2016	287 (8.6)
2017	283 (8.5)
2018	286 (8.6)
2019	98 (2.9)
Cohort
Chemicals in Our Bodies (CiOB)	402 (12.0)
Illinois Kids Development Studies (IKIDS)	184 (5.5)
Project Viva	842 (25.2)
Healthy Start	652 (19.5)
New Hampshire Birth Cohort Study (NHBCS)	324 (9.7)
Markers of Autism Risk in Babies Learning Early Signs (MARBLES)	39 (1.2)
Emory (Atlanta)	424 (12.7)
Maternal And Developmental Risks from Environmental and Social Stressors (MADRES)	347 (10.4)
Pregnancy and EnvironmenT And Lifestyle Study (PETALS)	124 (3.7)
Rochester	35 (1.0)
Kaiser Permanente Research Bank Pregnancy Cohort (KPRB-PC)	13 (0.4)

Note: BMI, body mass index; ECHO, Environmental influences on Child Health Outcomes; GED, General Educational Development; PSS, perceived stress scale; SD, standard deviation.

^a $n=\mathrm{2,009}$.

^b Small-, appropriate-, and large-for-gestational-age were defined, respectively, as singleton infants with weight $<10$th percentile, 10th–90th percentile, and $>90$th percentile of birthweight-for-gestational-age and sex using a 2017 U.S. reference population.

^c $n=\mathrm{3,219}$.