Skip to main content

Table 2 Relationship between VitD intake and obstetric outcomes among women who conceived without ART

From: Preconception vitamin D intake and obstetric outcomes in women using assisted reproductive technology: the Japan Environment and Children’s Study

  Quintile for VitD  
Q1 (low) Q2 Q3 Q4 Q5 (high) p-valuea
n = 17,687 n = 17,407 n = 17,254 n = 17,532 n = 17,415
VitD intake before pregnancy, μg/day, median (IQR) 1.4 (0.8–1.8) 3.0 (2.6–3.3) 4.3 (4.0–4.7) 6.0 (5.5–6.7) 10.2 (8.7–12.8)  
PTB at < 37 weeks
 Number, n 729 784 724 704 749  
 Occurrence, % 4.1 4.5 4.2 4.0 4.3 0.812
 aOR (95% CI) 0.97 (0.89–1.09) 1.08 (0.97–1.12) 1 (Ref) 0.95 (0.85–1.05) 1.02 (0.92–1.13)  
PTB at < 34 weeks
 Number, n 145 157 138 119 145  
 Occurrence, % 0.8 0.9 0.8 0.7 0.8 0.361
 aOR (95% CI) 1.02 (0.81–1.30) 1.14 (0.90–1.43) 1 (Ref) 0.85 (0.66–1.08) 1.05 (0.83–1.33)  
LBW < 2500 g
 Number, n 1371 1397 1264 1256 1352  
 Occurrence, % 7.8 8.0 7.3 7.2 7.8 0.198
 aOR (95% CI) 1.00 (0.92–1.09) 1.09 (1.01–1.18) 1 (Ref) 0.99 (0.91–1.07) 1.09 (1.00–1.18)  
LBW < 1500 g
 Number, n 79 91 68 66 73  
 Occurrence, % 0.4 0.5 0.4 0.4 0.4 0.203
 aOR (95% CI) 1.17 (0.84–1.63) 1.35 (0.98–1.87) 1 (Ref) 0.97 (0.69–1.37) 1.12 (0.80–1.56)  
SGA
 Number, n 868 860 777 851 963  
 Occurrence, % 4.9 5.0 4.5 4.9 5.6 0.025
 aOR (95% CI) 1.06 (0.96–1.17) 1.09 (0.99–1.21) 1 (Ref) 1.10 (0.99–1.22) 1.26 (1.14–1.39)  
HDP
 Number, n 415 394 357 377 364  
 Occurrence, % 2.4 2.3 2.1 2.2 2.1 0.076
 aOR (95% CI) 1.05 (0.91–1.22) 1.06 (0.92–1.23) 1 (Ref) 1.04 (0.90–1.21) 1.00 (0.86–1.16)  
  1. VitD Vitamin D, ART Assisted reproductive technology, IQR Interquartile range, PTB Preterm birth, aOR Adjusted odds ratio, CI Confidence interval, Ref Reference, LBW Low-birth weight infant, SGA Small for gestational age, HDP Hypertensive disorder of pregnancy
  2. aOR was calculated by logistic regression analysis, using maternal age (20–29 years old as the reference), body mass index before pregnancy, maternal smoking status, maternal education, endometriosis, parity, and daily calorie intake
  3. a Mantel–Haenszel’s chi-square test for linear trends