Table 1 Maternal medical background and obstetric outcomes per dietary Ca intake quintiles

Maternal medical background

 Ca intake before pregnancy mg/day median (inter-quartile range)

199 (154–235)

321 (295–347)

430 (401–460)

567 (529–613)

899 (755–1253)

< 0.001^a

 Maternal age, years mean (SD)

28.5 (5.1)

29.9 (5.1)

30.4 (5.0)

30.7 (4.9)

30.8 (5.1)

< 0.001^b

 Advanced maternal age, %

13.4

19.2

21.3

22.9

24.2

< 0.001^c

Pre-pregnancy BMI (kg/m²), %

 < 18.5

19.1

18.4

16.2

16.7

16.1

< 0.001^c

 18.5 to 25.0

71.4

72.4

75.3

75.0

76.2

 > 25.0

9.5

9.2

8.6

8.4

7.7

Smoking during pregnancy, %

5.5

3.5

3.1

2.6

2.7

< 0.001^c

Sterility treatment, %

7.3

10.7

10.8

11.5

12.2

< 0.001^c

Maternal education, year, %

 < 10

5.8

3.6

2.6

2.3

2.5

< 0.001^c

 10 to 12

36.7

29.9

25.8

24.3

24.8

 13 to 16

39.6

43.0

43.2

43.2

43.9

 more than 17

17.7

23.6

28.5

30.2

28.8

Household income, JPY, %

 <2,000,000

8.1

5.7

4.7

4.4

4.8

< 0.001^c

 2,000,000–5,999,999

69.5

66.4

65.6

64.1

64.1

 6,000,000–9,999,999

19.5

23.7

24.9

26.4

25.7

 ≥10,000,000

3.0

4.2

4.9

5.1

5.3

Obstetric outcome

 HDP, %

3.1

3.4

3.5

3.2

3.1

0.719^d

 Eo-HDP, %

0.5

0.7

0.5

0.5

0.6

0.739^d

 Lo-HDP, %

2.3

2.4

2.6

2.4

2.2

0.655^d

 PTB < 37 wks, %

4.4

3.9

4.5

4.2

4.0

0.322^d

 LBW < 2500 g, %

9.7

8.6

8.7

9.0

8.9

0.213^d