Table 1 Characteristics of mothers, fathers, infants, and childcare environments

Maternal characteristics

 Age (years)

31.4 ± 4.9

 Education level (years)

  ≤9

5 (3.2)

  10–12

54 (35.1)

  13–16

92 (59.7)

  ≥17

3 (1.9)

 Household income (yen/year)

  <3,000,000

26 (16.9)

  3,000,000–5,000,000

68 (44.2)

  5,000,000–7,000,000

40 (26.0)

  >7,000,000

20 (13.0)

 Worked during pregnancy

23 (14.9)

 Smoked during pregnancy

22 (14.3)

 Caffeine intake during pregnancy (mg/day)

123.4 (80.2–183.1)^a

 Alcohol intake during pregnancy (g/day)

0.0 (0.0–0.9)^a

 Stressful life events before pregnancy

60 (39.0)

 Self-reported psychological status

  Past depressive symptoms

18 (11.7)

  Worrying

70 (45.5)

  Obsessiveness

45 (29.2)

 Readiness for pregnancy

  Planned pregnancy

77 (50.0)

  Wanted pregnancy

131 (85.1)

 Worked at 6 months postpartum

17 (11.0)

Paternal characteristics

 Age (years)

33.2 ± 5.8

 Education level (years)

  ≤9

4 (2.6)

  10–12

53 (34.4)

  13–16

80 (51.9)

  ≥17

17 (11.0)

Infant characteristics

 Male

78 (50.6)

 First born (parity = 0)

71 (46.1)

 Preterm birth

5 (3.2)

 SGA

3 (1.9)

 LBW

3 (1.9)

 IUGR

12 (7.8)

 Gestational age (days)

275.7 ± 8.5

 Birth weight (g)

3,090.5 ± 361.1

 Length (cm)

48.3 ± 1.7

 Head circumference (cm)

33.3 ± 1.3

 Chest circumference (cm)

31.5 ± 1.4

 Age at 6-month assessment (days)

190.3 ± 8.7

Child care environment

 EES subscores at 6 months

  Humanistic involvement

7 (7–8)^a

  Responsiveness

2 (2–2)^a

  Avoidance of restriction and punishment

1 (1–1)^a

  Physical involvement

3 (2–3)^a

  Social involvement

4 (3–5)^a

  Organisation of environment

2 (2–3)^a

  Social support

5 (4–5)^a