Table 1 Demographic characteristics of mother-infant pairs in CMUBC

Mothers

 Age

   < 25

24

2.6

  25–29

305

33.6

  30–35

375

41.3

   > 35

204

22.5

 Nationality

  Han

756

83.3

  Others

152

16.7

 Educational level

  Junior high school and below

91

10.0

  High school and technical secondary school

70

7.7

 Bachelor degree/college or above

634

69.8

  Postgraduate or above

113

12.5

 household income yearly

   < 3

167

18.4

  3–5

417

46.0

  5–7

86

9.5

   > 7

238

26.1

 Gravidity

  1

409

45.1

  2

274

30.2

   ≥ 3

225

24.7

 Parity

  0

652

71.9

   ≥ 1

256

28.1

 Pre-pregnancy BMI(kg/m²)

   < 18.5

61

6.7

  18.5 < 23.9

438

48.3

  24.0 < 27.9

274

30.2

   ≥ 28.0

135

14.8

 GWG

  Insufficient

112

12.4

  Appropriate

344

37.8

  Redundancy

452

49.8

 Caesarean section

  Yes

426

46.9

  No

482

53.1

 Gestational age(week)

   < 37

84

9.3

   ≥ 37

824

90.7

 Gestational diabetes

  Yes

212

23.4

  No

696

76.3

 Gestational hypertension

  Yes

144

15.9

  No

774

84.1

Infants

 Sex

  Male

449

49.4

  Female

459

50.6

 Birth weight

   < 2500

95

10.5

  2500–3999

747

82.3

   ≥ 4000

66

7.2

 Growth Level

  GA

50

5.5

  AGA

782

86.1

  LGA

76

8.4