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Table 3 Univariable analysis of risk factors for low birth weight, 1997/98 São Luís birth cohort

From: Low birth weight in São Luís, northeastern Brazil: trends and associated factors

Variables

% Low birth weight

Odds ratio*

95% Confidence interval

p**

Newborn’s sex

   

0.701

 Male

7.4

1

Reference

 

 Female

7.8

1.06

(0.78; 1.43)

 

Preterm birth

   

<0.001

 Yes

31.6

10.42

(7.55; 14.38)

 

 No

4.2

1

Reference

 

IUGR***

   

<0.001

 No

3.1

1

Reference

 

 Mild

5.1

1.66

(0.81; 3.41)

 

 Moderate

11.9

4.23

(2.25; 7.97)

 

 Severe

74.3

90.34

(57.02; 143.12)

 

Maternal age (years)

   

0.005

 <18

12.9

2.00

(1.37; 2.93)

 

 18 – 19

6.6

0.95

(0.61; 1.47)

 

 20 – 34

6.9

1

Reference

 

 ≥35

6.9

1.00

(0.45; 2.22)

 

Maternal schooling (years)

   

0.197

 0 - 4

7.7

2.39

(0.82; 6.91)

 

 5 - 8

8.3

2.61

(0.94; 7.26)

 

 9 - 11

7.3

2.27

(0.81; 6.63)

 

 ≥12

3.4

1

Reference

 

Marital status

   

0.340

 Married

6.4

1

Reference

 

 Consensual union

8.2

1.30

(0.89; 1.88)

 

 Without a companion

8.0

1.27

(0.83; 1.94)

 

Family income (minimum wages)

   

0.073

 ≤1

9.3

1.25

(0.87; 1.78)

 

 1- 3

7.8

1.52

(1.00; 2.32)

 

 >3

6.3

1

Reference

 

 Missing

11.3

1.89

(1.09; 3.29)

 

Maternal smoking during pregnancy

   

0.036

 No

7.4

1

Reference

 

 Yes

13.5

1.95

(1.09; 3.50)

 

Occupation of the family head

   

0.677

 Non-manual

6.8

1

Reference

 

 Skilled manual worker

7.9

1.18

(0.78; 1.78)

 

 Unskilled manual worker

7.4

1.10

(0.70; 1.70)

 

 Missing

10.8

1.65

(0.70; 3.90)

 

Parity

   

0.001

 1

9.6

1.72

(1.19; 2.48)

 

 2

5.8

1

Reference

 

 ≥3

5.5

0.94

(0.57; 1.53)

 

Adequacy of prenatal care use

   

0.850

 Adequate

7.9

1

Reference

 

 Inadequate

7.1

0.89

(0.64; 1.23)

 

 No care

8.5

1.09

(0.63; 1.87)

 

 Missing

8.6

1.09

(0.33; 3.64)

 

Category of delivery care

   

0.133

 Private

4.5

1

Reference

 

 Public

8.0

1.45

(0.87; 2.43)

 

Type of delivery

   

0.027

 Vaginal

7.5

1

Reference

 

 Cesarean

7.9

1.85

(1.02; 3.38)

 
  1. *Odds Ratio (OR) calculated by simple logistic regression.
  2. **p-value calculated by the log likelihood ratio test.
  3. ***IUGR–intrauterine growth restriction based on the birth weight ratio.