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Table 5 Timing of folic acid supplementation and risk of spontaneous preterm delivery (sPTD)

From: Retracted: Folic acid supplementation, dietary folate intake during pregnancy and risk for spontaneous preterm delivery: a prospective observational cohort study

sPTD Time of olic acid   Unadjusted Adjusted1
  supplementation n HR (CI) p HR (CI) p
  >8 w pre-conceptional 428 1.16 (1.04–1.30) 0.01 1.16 (1.02–1.31) 0.02
All 0-8 w pre-conceptional 572 1.02 (0.93–1.13) 0.64 1.04 (0.92–1.17) 0.52
  1st trimester 1185 0.94 (0.84–1.05) 0.25 0.88 (0.78–0.99) 0.04
  2nd trimester 795 1.11 (1.01–1.23) 0.03 1.10 (0.99–1.21) 0.08
  >8 w pre-conceptional 79 1.39 (1.07–1.80) 0.01 1.34 (0.99–1.80) 0.06
Early 0-8 w pre-conceptional 103 1.21 (0.94–1.55) 0.13 1.18 (0.88–1.58) 0.26
  1st trimester 199 1.07 (0.81–1.42) 0.62 0.94 (0.69–1.28) 0.67
  2nd trimester 137 1.26 (0.99–1.60) 0.06 1.18 (0.91–1.51) 0.21
  >8 w pre-conceptional 349 1.12 (0.99–1.27) 0.07 1.13 (0.98–1.29) 0.09
Late 0-8 w pre-conceptional 469 0.99 (0.89–1.11) 0.88 1.01 (0.89–1.15) 0.84
  1st trimester 986 0.91 (0.81–1.03) 0.14 0.87 (0.76–0.99) 0.04
  2nd trimester 658 1.09 (0.98–1.21) 0.13 1.08 (0.97–1.21) 0.17
  1. Folic acid supplementation at different times (Q1 and Q3 data) and hazard ratios for spontaneous PTD (n = 1,628 for 22+0-36+6 weeks, n = 264 for early (22+0-33+6), n = 1,364 for late (34+0-36+6)). Cox regression for 65,668 participants in the Norwegian Mother and Child Cohort Study (2002 – 2009). Iatrogenic deliveries have been censored in the regression model.
  2. 1 Cox regression, adjusted for maternal age, prepregnancy BMI, parity, history of PTD and spontaneous abortion, child’s sex, smoking habits and alcohol consumption during pregnancy, maternal education, marital status, household income, energy intake and dietary folate intake. Mutual adjustment for folic acid supplementation at other time points.