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Table 2 Stratified meta-analysis of caffeine intake (per 100-mg/day increment) and risk of low birth weight/IUGR/SGA

From: Maternal caffeine intake during pregnancy is associated with risk of low birth weight: a systematic review and dose-response meta-analysis

Characteristics

Number of studies

Summary RR (95% CI)

P-for-difference

P-for-heterogeneity

I 2(95% CI)

All studies

9

1.13 (1.06 to 1.21)

 

<0.01

82.4 (65.4 to 89.1)

Region

     

 United States

4

1.20 (0.95 to 1.52)

Ref.

0.01

75.5 (32.3 to 91.1)

 Europe

5

1.12 (1.05 to 1.19)

0.60

<0.01

87.2 (69.2 to 92.7)

Year of publication

     

 In or after 2000

5

1.10 (1.04 to1.16)

0.29a

0.07

53.9 (0.0 to 81.0)

 Before 2000

4

1.27 (1.02 to 1.58)

 

<0.01

89.1 (74.8 to 95.3)

Study population

     

 ≥2,500

6

1.11 (1.04 to1.18)

Ref.

<0.01

86.0 (68.9 to 91.8)

 <2,500

3

1.28 (1.14 to 1.44)

0.25

0.45

0.0 (0.0 to 89.6)

Study design

     

 Cohort

8

1.11 (1.04 to 1.18)

Ref.

<0.01

81.0 (59.1 to 88.7)

 Nested case-control

1

1.33 (1.16 to 1.52)

0.21

-

-

Exposure

     

 Caffeine

7

1.13 (1.06 to 1.21)

Ref.

0.01

67.4 (0.0 to 83.4)

 Coffee

2

1.16 (0.91 to 1.48)

0.93

<0.01

91.9 (NA)

Outcome b

     

 LBW

5

1.12 (1.02 to 1.23)

Ref.

<0.01

75.8 (40.6 to 90.1)

 IUGR

5

1.12 (1.00 to 1.25)

0.78

0.04

59.5 (0.0 to 82.8)

 SGA

2

1.13 (1.07 to 1.18)

0.85

0.14

53.9 (NA)

Age c

     

 <30 years

4

1.17 (1.05 to 1.31)

Ref.

<0.01

88.6 (73.4 to 95.1)

 ≥30 years

5

1.13 (1.08 to 1.19)

0.54

0.32

15.1 (0.0 to 69.2)

Method of exposure assessment

     

 Interviewer-based

5

1.17 (1.01 to 1.36)

Ref.

0.01

68.2 (17.9 to 87.7)

 Self-administered

3

1.08 (1.01 to 1.16)

0.42

<0.01

90.7 (70.5 to 95.2)

 NA

1

1.33 (1.16 to 1.52)

0.38

-

-

Exposure period assessed b

     

 First trimester

3

1.17 (0.90 to 1.53)

Ref.

<0.01

83.0 (48.0 to 94.4)

 First to second trimesters

2

1.09 (0.99 to 1.21)

0.62

<0.01

95.3 (NA)

 Whole pregnancy

2

1.13 (1.04 to 1.24)

0.99

0.40

0.0 (NA)

 Third trimester

2

1.06 (1.00 to 1.12)

0.64

0.63

0.0 (NA)

 NA

1

1.33 (1.16 to 1.52)

0.51

-

-

Adjustment for smoking d

     

 Fine

7

1.12 (1.04 to 1.20)

Ref.

<0.01

82.0 (59.1 to 89.6)

 Crude

2

1.24 (0.89 to 1.72)

0.52

<0.01

91.7 (NA)

Median population caffeine intake

     

 <200 mg/d

5

1.15 (1.05 to 1.26)

0.32a

0.02

66.7 (0.0 to 85.1)

 ≥200 mg/d

3

1.10 (1.01 to 1.21)

 

<0.01

83.9 (51.8 to 94.7)

 NA

1

1.40 (0.84 to 2.32)

 

-

-

  1. a P-value was obtained by modeling year of publication and median of assigned doses as continuous variables; btotal number of study is more than 9 because some studies reported additional (usable) results for a different outcome or exposure period; cmean age <30 years or ≥30 years. If mean age is not available, classification was based on whether the majority of the population (>50%) is <30 years or ≥30 years; dfine adjustment for smoking refers to studies that adjusted for amount of smoking or studies that adjusted for smoking using a biomarker; crude adjustment refers to studies that did not adjust for amount of smoking. I 2, I-squared; IUGR, intrauterine growth restriction; LBW, low birth weight; NA, not available; Ref., reference. RR, relative risk; SGA, small for gestational age.
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BMC Medicine

ISSN: 1741-7015

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