Table 1 Child and family characteristics for infants born in Taiwan in 2004–2014 (n = 2,206,441)

Birth year

 2004–2009

1,206,470

54.7

 2010–2014

999,971

45.3

Gender

 Female

1,057,017

47.9

 Male

1,149,424

52.1

Birthweight (g)^a

 ≥ 2500

1,950,802

88.4

 2000–2499

123,595

5.6

 < 2000

34,357

1.6

Maternal marital status^b

 Married

1,952,262

88.5

 Single

84,403

3.8

 Others (e.g., divorced and widowed)

43,480

2.0

 Missing

237,407

10.8

Having at least one older child^c

 No

1,632,757

74.0

 Yes

573,684

26.0

Income level (insurance status)^d

 Low income/poverty

542,842

24.6

 Middle income

1,121,927

50.9

 High income

541,672

24.6

Maternal educational attainment^a

 Junior high school or below

342,608

15.5

 Senior high school

694,496

31.5

 College or above

1,119,503

50.7

Maternal age at having the index child (years)^a

 35 or above

41,168

1.9

 20–34

1,776,026

80.5

 < 20

341,394

15.5

Well-child care utilization in the first two months of life^d

 Yes

1,793,892

81.3

 No

412,549

18.7

Maternal depression ^d,e

 No

2,194,753

99.5

 Yes

11,688

0.5

Maternal substance use-related problems ^d,e

 No

2,205,747

99.97

 Yes

694

0.03

ICD-9-CM (per 1,000)^d

 Maltreatment-related injuries^f

6297

2.85

  Maltreatment syndrome

579

0.26

  Assaults

166

0.08

  Undetermined causes

5580

2.52

Death within three months of index visits (per 1,000)^g

50

7.94

Death within three years of follow-up (per 100)^g

79

1.25