Table 1.

Characteristics of sample (N = 2938)

Variables	n (%)
Household characteristics
Household income per capita (RMB) (mean, s.d)	11,482 (28,446)
Residential regions
Eastern China	1172 (39.9)
Central China	852 (29.0)
Western China	914 (31.1)
Residence
Urban	990 (33.7)
Rural	1948 (66.3)
Parental characteristics
Mother’s educational status
Middle school and below	2058 (70.1)
High school or above	738 (25.1)
Missing data	142 (4.8)
Father’s educational status
Middle school and below	1951 (66.4)
High school or above	800 (27.2)
Missing data	187 (6.4)
ISEI score for mother’s occupation
16–32/unemployment	2079 (70.8)
33–43	480 (16.3)
44–58	256 (8.7)
59–90	123 (4.2)
ISEI score for father’s occupation
16–32/unemployment	2011 (68.5)
33–43	564 (19.2)
44–58	218 (7.4)
59–90	145 (4.9)
Mother’s marital status
Single	44 (1.5)
Married	2864 (97.5)
Divorced/widowed	22 (0.7)
Missing data	8 (0.3)
Parity
Primipara	1653 (56.3)
Multipara	1285 (43.7)
Age of mother (years) (mean, s.d)	27.35 (4.79)
Age of father (years) (mean, s.d)	29.37 (5.09)
Infant characteristics
Breastfeeding duration (months) (mean, s.d)	8.66 (6.15)
Gender
Male	1549 (52.7)
Female	1389 (47.3)
Place of delivery
Health facility	2767 (94.2)
Others	129 (4.4)
Missing data	42 (1.4)
Ethnicity
Han	2590 (88.2)
Minority	348 (11.8)
Birth weight
Below 2500 g	126 (4.3)
Normal	2495 (84.9)
Above 4000 g	245 (8.3)
Missing data	72 (2.5)
Gestational age (weeks)
Less than 37	1490 (50.7)
37–42	1343 (45.7)
Over 42	52 (1.8)
Missing data	53 (1.8)
Birth year
2010	713 (24.3)
2011	692 (23.6)
2012	648 (22.0)
2013	549 (18.7)
2014	336 (11.4)

The ISEI score refers to occupational status, with higher values indicating higher occupational status