Table 1 Distribution of selected characteristics in 1565 mother-child pairs

Baseline characteristics

  Maternal age, years, mean ±SD

31.3 ± 4.2

  Region of residence

   Fukuoka Prefecture

883 (56.4)

   Prefecture on Kyushu Island other than Fukuoka

527 (33.7)

   Okinawa Prefecture

155 (9.9)

  Number of living children already born to same mother

   0

615 (39.3)

   1

633 (40.5)

   ≥ 2

317 (20.3)

  Nuclear family structure

1336 (85.4)

  Maternal education, years

   < 13

 361 (23.1)

   13 − 14

 523 (33.4)

   ≥ 15

 681 (43.5)

  Maternal employment^a

 943 (60.3)

  Alcohol consumption during the preceding month

 209 (13.4)

  Body mass index, kg/m², mean ± SD

 21.4 ± 2.7

Infant characteristics at birth

  Birth weight, g, mean ± SD

3006.3 ± 395.5

  Gestational age, weeks, mean ± SD

38.9 ± 1.5

  Male gender

762 (48.7)

  Low birth weight (< 2500 g)

120 (7.7)

  Preterm birth (< 37 weeks)

 62 (4.0)

  Small-for-gestational-age (< 10th percentile)

122 (7.8)