Table 1.

Descriptive characteristics of study participants and child neurodevelopment measures (Bayley scores at 2 years of age) from a birth cohort study in Wuhan, China, 2014–2017 ($N=\mathrm{1,041}$ mother–child pairs).

Characteristic	$N$ (%) or $\text{mean}\pm \text{SD}$	MDI scores		PDI scores
		$\text{Mean}\pm \text{SD}$	$p$-Value	$\text{Mean}\pm \text{SD}$	$p$-Value
Total	1,041	$110\pm 21.8$	—	$111\pm 17.1$	—
Maternal characteristics
Age at delivery (y)	$29.4\pm 3.7$	—	0.24	—	0.25
$<25$	60 (5.80)	$106\pm 19.5$	—	$114\pm 15.1$	—
25–29	548 (52.6)	$110\pm 22.2$	—	$110\pm 17.0$	—
30–34	330 (31.7)	$111\pm 21.3$	—	$112\pm 17.7$	—
$\ge 35$	103 (9.90)	$107\pm 21.8$	—	$109\pm 16.1$	—
PBMI (${\mathrm{kg}/\mathrm{m}}^2$)	$21.1\pm 2.91$	—	0.14	—	0.90
$<18.5$	195 (18.7)	$111\pm 20.4$	—	$111\pm 16.6$	—
18.5–23.9	694 (66.7)	$110\pm 22.0$	—	$111\pm 17.3$	—
$\ge 24$	152 (14.6)	$107\pm 22.1$	—	$111\pm 16.8$	—
Maternal education level	—	—	$<0.0001$	—	0.36
$\le \text{High-school degree}$	214 (20.6)	$104\pm 21.7$	—	$110\pm 17.6$	—
Bachelor’s degree	763 (73.3)	$111\pm 22.0$	—	$111\pm 16.9$	—
$\ge \text{Master}’\mathrm{s}\text{\hspace{0.17em}\hspace{0.17em}degree}$	64 (6.1)	$118\pm 14.6$	—	$114\pm 17.4$	—
Household income (CNY)	—	—	0.07	—	0.20
$<\mathrm{50,000}$	120 (11.5)	$109\pm 23.4$	—	$110\pm 15.7$	—
50,000–100,000	384 (36.9)	$108\pm 21.7$	—	$110\pm 18.0$	—
$\ge \mathrm{100,000}$	537 (51.6)	$111\pm 21.2$	—	$112\pm 16.7$	—
Parity	—	—	0.007	—	0.05
Nulliparous	806 (77.4)	$111\pm 21.8$	—	$110\pm 16.9$	—
Multiparous	235 (22.6)	$106\pm 21.4$	—	$113\pm 17.6$	—
Delivery mode	—	—	$<0.0001$	—	0.007
Vaginal delivery	507 (48.7)	$113\pm 22.0$	—	$112\pm 17.0$	—
Cesarean delivery	534 (51.3)	$107\pm 22.7$	—	$110\pm 17.0$	—
GWG categories according to NHC	—	—	0.88	—	0.77
Inadequate total GWG	165 (15.9)	$111\pm 22.0$	—	$110\pm 17.7$	—
Adequate total GWG	429 (41.2)	$110\pm 22.0$	—	$111\pm 17.7$	—
Excessive total GWG	447 (42.9)	$110\pm 21.5$	—	$111\pm 16.2$	—
Passive smoking during pregnancy	—	—	0.37	—	0.88
Yes	261 (25.1)	$109\pm 22.2$	—	$111\pm 18.6$	—
No	780 (74.9)	$110\pm 21.6$	—	$111\pm 16.4$	—
Folic acid supplementation during pregnancy	—	—	0.51	—	0.97
Yes	912 (87.6)	$110\pm 21.9$	—	$111\pm 17.1$	—
No	129 (12.4)	$109\pm 21.2$	—	$111\pm 16.5$	—
Maternal anemia	—	—	0.71	—	0.65
Yes	42 (4.0)	$109\pm 21.4$	—	$110\pm 15.8$	—
No	999 (96.0)	$110\pm 21.8$	—	$111\pm 17.1$	—
Hypertension in pregnancy	—	—	0.83	—	0.28
Yes	24 (2.30)	$109\pm 23.4$	—	$107\pm 15.5$	—
No	1,017 (97.7)	$110\pm 21.7$	—	$111\pm 17.1$	—
Gestational diabetes	—	—	0.35	—	0.70
Yes	98 (9.40)	$108\pm 23.1$	—	$112\pm 18.1$	—
No	943 (90.6)	$110\pm 21.6$	—	$111\pm 17.0$	—
Sampling season
First trimester	—	—	0.32	—	0.003
Warm season	523 (50.2)	$111\pm 21.8$	—	$109\pm 17.5$	—
Cold season	518 (49.8)	$109\pm 21.7$	—	$113\pm 16.4$	—
Second trimester	—	—	0.41	—	0.69
Warm season	499 (47.9)	$110\pm 22.2$	—	$111\pm 17.6$	—
Cold season	542 (52.1)	$109\pm 21.4$	—	$111\pm 16.6$	—
Third trimester	—	—	0.50	—	0.001
Warm season	530 (50.9)	$110\pm 21.7$	—	$113\pm 17.6$	—
Cold season	511 (49.1)	$109\pm 21.9$	—	$109\pm 16.3$	—
Paternal education level	—	—	0.004	—	0.49
$\le \text{High-school degree}$	209 (20.1)	$106\pm 22.5$	—	$110\pm 18.1$	—
Bachelor’s degree	783 (75.2)	$111\pm 21.6$	—	$111\pm 16.8$	—
$\ge \text{Master}’\mathrm{s}\text{\hspace{0.17em}\hspace{0.17em}degree}$	49 (4.70)	$114\pm 19.5$	—	$113\pm 16.2$	—
Child characteristics
Child’s sex	—	—	$<0.0001$	—	0.11
Boy	553 (53.1)	$107\pm 23.3$	—	$110\pm 17.2$	—
Girl	488 (46.9)	$113\pm 19.4$	—	$112\pm 16.9$	—
Birth weight (g)	$\mathrm{3,355}\pm 424$	—	0.23	—	0.38
$<\mathrm{2,500}$ (low birth weight)	21 (2.02)	$107\pm 26.0$	—	$106\pm 15.1$	—
2,500–4,000	956 (91.8)	$110\pm 21.5$	—	$111\pm 17.2$	—
$>\mathrm{4,000}$	64 (6.15)	$106\pm 24.0$	—	$111\pm 16.2$	—
Gestational age (wk)	$39.4\pm 1.1$	—	0.62	—	0.39
$<37$ (preterm birth)	28 (2.70)	$112\pm 19.1$	—	$109\pm 11.6$	—
$\ge 37$	1,013 (97.3)	$110\pm 21.8$	—	$111\pm 17.2$	—
Breastfeeding duration (months)	—	—	0.04	—	0.41
$<6$	437 (43.2)	$108\pm 22.1$	—	$112\pm 17.3$	—
$\ge 6$	574 (56.7)	$111\pm 21.5$	—	$110\pm 16.8$	—
Missing	30	—	—	—	—

Note: Values are $\text{mean}\pm \text{SD}$ or numbers (percentage). —, Not applicable; %, percentage; cold season, November–April; GWG, gestational weight gain; MDI, mental development index; NHC, National Health Commission of the People’s Republic of China; PBMI, prepregnancy body mass index; PDI, psychomotor development index; SD, standard deviation; SD, standard deviation; warm season, May–October. *$p$-Values were derived from the analysis of variance performed to compare MDI and PDI among different characteristic categories. $p$-Values of $<0.05$ were considered statistically significant.