Table 1 Characteristics of participants

N

361

25

Age, years

31.8 ± 5.1 (20–49)

33.8 ± 5.7 (20–44)

0.06

Primipara

180 (49.9)

10 (40.0)

0.34

Height, cm

158.6 ± 5.8 (145.0–175.0)

156.4 ± 4.3 (148.0–165.0)

0.07

Pre-pregnancy body mass index, kg/m²

21.0 ± 2.9 (14.7–37.7)

19.7 ± 2.1 (15.2–24.0)

0.044

Gestational weight gain, kg

10.0 ± 4.0 (− 3.7–21.0)

8.6 ± 3.7 (− 1.4–15.0)

0.08

Household income, yen

 < 2 million

11 (3.0)

1 (4.0)

0.98

 2–6 million

211 (58.4)

15 (60.0)

 ≥ 6 million

114 (31.6)

7 (28.0)

 Unknown

25 (6.9)

2 (8.0)

Educational level

 Junior high school

6 (1.7)

1 (4.0)

0.24

 High school

65 (18.0)

7 (28.0)

 Some college

135 (37.4)

11 (44.0)

 University

155 (42.9)

6 (24.0)

Alcohol drinking

 In conception, yes

100 (27.7)

4 (16.0)

0.46

 During pregnancy, yes

0 (0)

0 (0)

–

Drug

 In conception, yes

0 (0)

0 (0)

–

 During pregnancy, yes

0 (0)

0 (0)

–

Infants

 Gender, female

161 (44.6)

17 (68.0)

0.023

 Gestational day, week

39.0 ± 1.1 (37–41)

37.8 ± 0.7 (37–39)

< 0.001

 Birth weight, g

3056 ± 316 (2506–3994)

2362 ± 136 (1982–2606)

< 0.001