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Table 3 Relationship between VitD intake and obstetric outcomes among women who conceived with 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 = 383 n = 530 n = 578 n = 587 n = 516
VitD intake before pregnancy, μg/day, median (IQR) 1.5 (1.0–1.9) 3.0 (2.6–3.3) 4.3 (4.0–4.7) 6.0 (5.4–6.6) 10.0 (8.5–12.1)  
PTB at < 37 weeks
 Number, n 30 35 29 40 50  
 Occurrence, % 7.8 6,6 5.0 6.8 9.7 0.206
 aOR (95% CI) 1.64 (0.96–2.78) 1.32 (0.79–2.20) 1 (Ref) 1.41 (0.86–2.30) 2.05 (1.27–3.31)  
PTB at < 34 weeks
 Number, n 7 9 7 14 13  
 Occurrence, % 1.8 1.7 1.2 2.4 2.5 0.251
 aOR (95% CI) 1.50 (0.52–4.34) 1.37 (0.50–3.72) 1 (Ref) 2.03 (0.81–5.09) 1.90 (0.74–4.87)  
LBW < 2500 g
 Number, n 45 50 52 50 57  
 Occurrence, % 11.7 9.4 9.0 8.5 11.1 0.727
 aOR (95% CI) 1.30 (0.85–2.00) 1.04 (0.69–1.57) 1 (Ref) 0.97 (0.65–1.46) 1.27 (0.85–1.89)  
LBW < 1500 g
 Number, n 8 7 5 8 9  
 Occurrence, % 2.1 1.3 0.9 1.4 1.8 0.850
 aOR (95% CI) 2.36 (0.76–7.33) 1.45 (0.45–4.64) 1 (Ref) 1.63 (0.53–5.04) 1.79 (0.58–5.54)  
SGA
 Number, n 26 28 32 32 20  
 Occurrence, % 6.8 5.3 5.5 5.5 3.9 0.105
 aOR (95% CI) 1.21 (0.70–2.09) 0.94 (0.55–1.60) 1 (Ref) 1.01 (0.61–1.68) 0.65 (0.36–1.17)  
HDP
 Number, n 19 28 27 31 24  
 Occurrence, % 5.0 5.3 4.7 5.3 4.7 0.841
 aOR (95% CI) 1.01 (0.55–1.84) 1.00 (0.57–1.74) 1 (Ref) 1.16 (0.68–1.97) 0.93 (0.53–1.65)  
  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 as 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