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Table 3 Associations between tea consumption and risk of preterm birth by duration and starting age of tea consumption (n = 10 179), Urban China, 2010–2012

From: Maternal tea consumption and the risk of preterm delivery in urban China: a birth cohort study

Drink tea Term (n) Preterm (n = 1019) Moderate preterm (n = 833) Very preterm (n = 186) Medically indicated (n = 338) Spontaneous (n = 68)
No. OR(95 % CI) No. OR(95 % CI) No. OR(95 % CI) No. OR(95 % CI) No. OR(95 % CI)
Never 8403 900 1 733 1 167 1 295 1 605 1
Ever            
 Duration, month            
   ≤ 48 321 48 1.24(0.89–1.73) 36 1.16(0.80–1.68) 12 1.52(0.83–2.83) 22 1.61(0.95–2.73) 26 1.08(0.70–1.64)
   > 48 304 52 1.49(1.08–2.04) 46 1.62(1.16–2.27) 6 0.84(0.36–1.94) 17 1.14(0.63–2.07) 35 1.65(1.14–2.39)
    P for trend   0.008 0.0028 0.65 0.26 0.012
 Start drinking tea age, year            
   < 20 272 55 1.60(1.17–2.20) 48 1.76(1.26–2.46) 7 0.95(0.43–2.08) 20 1.68(0.97–2.91) 35 1.64(1.13–2.39)
   ≥ 20 340 46 1.31(0.94–1.83) 39 1.35(0.94–1.94) 7 1.03(0.47–2.26) 14 0.95(0.51–1.80) 32 1.48(1.01–2.17)
  1. Adjusted for maternal age, educational level, employ status, monthly family income, parity, hypertensive disorder complicating pregnancy, prepregnancy BMI, alcohol drinking and smoking (active smoking and passive smoking) during pregnancy and history of preterm
  2. Abbreviation: BMI body mass index