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

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

 

Time of folic acid supplementation

sPTD

Unadjusted

Adjusted 1

  

n

HR

(CI)

p

HR

(CI)

p

All

>8 w preconception

478

1.17

(1.06; 1.30)

0.003

1.17

(1.04; 1.32)

0.01

 

0-8 w preconception

648

1.01

(0.92; 1.12)

0.80

1.01

(0.90; 1.13)

0.84

 

1st trimester

1326

0.94

(0.84; 1.05)

0.26

0.89

(0.79; 1.00)

0.05

 

2nd trimester

869

1.10

(1.00; 1.21)

0.04

1.08

(0.98; 1.19)

0.11

Early

>8 w preconception

108

1.49

(1.19; 1.88)

0.001

1.51

(1.16; 1.97)

0.002

 

0-8 w preconception

133

1.15

(0.92; 1.43)

0.23

1.03

(0.80; 1.34)

0.81

 

1st trimester

262

1.11

(0.85; 1.44)

0.45

0.99

(0.74; 1.32)

0.95

 

2nd trimester

173

1.21

(0.97; 1.49)

0.09

1.12

(0.89; 1.39)

0.34

Late

>8 w preconception

370

1.10

(0.98; 1.24)

0.10

1.10

(0.97; 1.26)

0.15

 

0-8 w preconception

515

0.98

(0.88; 1.09)

0.69

1.00

(0.88; 1.13)

0.94

 

1st trimester

1064

0.91

(0.81; 1.03)

0.13

0.87

(0.76; 1.00)

0.04

 

2nd trimester

696

1.08

(0.98; 1.20)

0.13

1.08

(0.97; 1.20)

0.17

  1. Folic acid supplementation at different times (Q1 and Q3 data) and hazard ratios (HR) for spontaneous PTD (n = 1.755 for 22+0-36+6 weeks, n = 334 for early (22+0-33+6 weeks), n = 1,421 for late (34+0-36+6 weeks)) as compared to no intake at that time of pregnancy. Cox regression for 66,014 participants in the Norwegian Mother and Child Cohort Study (2002 – 2009). Iatrogenic deliveries have been censored in the regression model.
  2. 1Cox 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.