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Table 1 Comparison of key variables at study baseline between those selected into the study and those not selected from the Adolescent Study

From: Prenatal polychlorinated biphenyl exposure is associated with decreased gestational length but not birth weight: archived samples from the Child Health and Development Studies pregnancy cohort

Variable

Selected (N = 600)

Not Selected (N = 1420)

 

N

Mean

Std

N

Mean

Std

p-value

Birth weight (g)

600

3387.8

493.3

1420

3353.7

533.0

0.92

Gestation (days; LMP to term)

600

282.1

12.7

1404

279.1

16.3

<.001

Number of Previous Live Births

600

1.7

1.7

1420

1.9

1.8

0.09

 

N

%

 

N

%

 

p-value

Male

300

50.0

 

703

49.5

 

0.84

Mother Education at Child’s Birth

       

 < High School

74

12.3

 

169

11.9

 

0.58

 High School Graduate

202

33.7

 

477

33.6

  

 Some College/Trade School

200

33.3

 

444

31.3

  

 College Graduate or Higher

123

20.5

 

329

23.2

  

 Missing

1

0.2

 

1

0.1

  

Maternal Smoking During Pregnancy

       

 Never Smoked

315

52.5

 

662

46.6

 

0.16

 Smokes Now

180

30.0

 

490

34.5

  

 Smoked Until Current Pregnancy

40

6.7

 

119

8.4

  

 Former Smoker

61

10.2

 

136

9.6

  

 Missing

4

0.7

 

13

0.9

  
  1. Data are presented as number, (N), mean and standard deviation (std).