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

From: Association between pre-pregnancy calcium intake and hypertensive disorders during the first pregnancy: the Japan environment and children’s study

Variable Quintile for Ca p-value
Q1 (low) Q2 Q3 Q4 Q5 (High)
n = 6829 n = 6733 n = 6800 n = 6763 n = 6769
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) < 0.001a
 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) < 0.001b
 Advanced maternal age, % 13.4 19.2 21.3 22.9 24.2 < 0.001c
Pre-pregnancy BMI (kg/m2), %
 < 18.5 19.1 18.4 16.2 16.7 16.1 < 0.001c
 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 < 0.001c
Sterility treatment, % 7.3 10.7 10.8 11.5 12.2 < 0.001c
Maternal education, year, %
 < 10 5.8 3.6 2.6 2.3 2.5 < 0.001c
 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 < 0.001c
 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 0.719d
 Eo-HDP, % 0.5 0.7 0.5 0.5 0.6 0.739d
 Lo-HDP, % 2.3 2.4 2.6 2.4 2.2 0.655d
 PTB < 37 wks, % 4.4 3.9 4.5 4.2 4.0 0.322d
 LBW < 2500 g, % 9.7 8.6 8.7 9.0 8.9 0.213d
  1. BMI Body mass index, Ca Calcium, Eo Early onset, HDP Hypertensive disorder of pregnancy, JPY Japanese Yen, LBW Low birthweight, Lo Late onset, PTB Preterm birth, SD Standard deviation
  2. ap-value, Kruskal-Wallis analysis
  3. bp-value, one-way analysis of variance
  4. cp-value, chi-square test
  5. dp-value, the extended Mantel-Haenszel chi-square test