Table 1 Maternal characteristics 6691282165####

Age at delivery (years), mean ± SD

31.9 ± 4.8

31.2 ± 5.1

< 0.01

<25

295 (6.3)

10,125 (9.8)

25–<30

1,206 (25.8)

27,760 (26.9)

30–<35

1,732 (37.0)

35,650 (34.6)

≥35

1,450 (31.0)

27,414 (26.6)

Missing

0 (0.0)

2,111 (2.0)

Education (years)

< 0.01

<10

144 (3.1)

4,726 (4.6)

10–<13

2,558 (54.6)

54,579 (53)

13–<17

1,867 (39.9)

36,740 (35.6)

≥17

74 (1.6)

1,434 (1.4)

Missing

40 (0.9)

5,581 (5.4)

Parity

< 0.01

0

2,080 (44.4)

40,395 (39.2)

≥1

2,603 (55.6)

59,642 (57.9)

Missing

0 (0.0)

3,023 (2.9)

Prepregnancy BMI (kg/m²), mean ± SD

20.5 ± 2.9

21.2 ± 3.3

< 0.01

<25

1,082 (23.1)

16,629 (16.1)

25–<30

3,271 (69.8)

74,816 (72.6)

≥30

329 (7.0)

10,939 (10.6)

Missing

1 (0.0)

676 (0.7)

Annual household income

(million Japanese yen)

< 0.01

<2

210 (4.5)

5,167 (5.0)

2–<4

1,425 (30.4)

31,460 (30.5)

4–<6

1,453 (31.0)

30,082 (29.2)

6–<8

750 (16.0)

14,486 (14.1)

8–<10

302 (6.4)

5,954 (5.8)

≥10

207 (4.4)

3,888 (3.8)

Missing

336 (7.2)

12,023 (11.7)

Smoking status

< 0.01

Never smoked

2,897 (61.9)

56,156 (54.5)

Quit before pregnancy

1,008 (21.5)

23,280 (22.6)

Smoked in early pregnancy

732 (15.6)

17,791 (17.3)

Missing

46 (1.0)

5,833 (5.7)

Alcohol consumption

0.26

Never consumed

1,607 (34.3)

32,615 (31.6)

Stopped consuming before pregnancy

770 (16.4)

16,740 (16.2)

Consumed in early pregnancy

2,264 (48.3)

47,865 (46.4)

Missing

42 (0.9)

5,840 (5.7)

Hypertensive disorders of pregnancy

348 (7.4)

3,145 (3.1)

< 0.01

Missing

0 (0.0)

2,375 (2.3)

Gestational diabetes mellitus

48 (1.0)

2,713 (2.6)

< 0.01

Missing

0 (0.0)

2,375 (2.3)

Diabetes mellitus

133 (2.8)

1,101 (1.1)

< 0.01

Missing

0 (0.0)

2,375 (2.3)