Table 5 The results of univariate and multivariate linear regression tests in determining the relationship between addiction, lead concentration in mother’s blood and umbilical cord blood with outcomes of weight and 1-minute and 5 min Apgar scores

Birth weight (gr)

Univariate regression

Multivariate regression

Variables

B

Beta

95% CI

P value

B

Beta

95% CI

P value

Lower Bound

Upper Bound

Lower Bound

Upper Bound

(Constant)

3040.61

2869.94

3211.28

< 0.0001

Addiction

Yes

-541.

-0.58

-725.12

-357.6

< 0.0001

− 695.02

− 0.74

-1000.66

-381.39

< 0.0001

No

reference

Maternal blood lead (µg/dL)

-16.43

-0.38

-25.95

-6.91

0.001

10.02

0.23

-11.15

31.19

0.34

Umbilical cord blood lead (µg/dL)

-22.15

− 0.39

-34.58

-9.71

< 0.0001

-1.6

-0.02

-28.3

25.04

0.9

1-minute Apgar score

Univariate regression

Multivariate regression

Variables

B

Beta

95% CI

P value

B

Beta

95% CI

P value

Lower Bound

Upper Bound

Lower Bound

Upper Bound

(Constant)

8.39

7.96

8.81

< 0.0001

Addiction

Yes

-1.48

-0.23

-1.95

-1.02

< 0.0001

-1.16

-0.47

-1.94

-0.37

0.004

No

reference

Maternal blood lead (µg/dL)

-0.06

− 0.56

-0.08

-0.04

< 0.0001

-0.04

− 0.44

-0.1

0.004

0.06

Umbilical cord blood lead (µg/dL)

-0.07

-0.48

-0.1

− 0.04

< 0.0001

0.04

0.28

-0.02

0.1

0.21

5-minute Apgar score

Univariate regression

Multivariate regression

Variables

B

Beta

95% CI

P value

B

Beta

95% CI

P value

Lower Bound

Upper Bound

Lower Bound

Upper Bound

(Constant)

8.9

8.51

9.3

< 0.0001

Addiction

Yes

-1.14

-0.54

-1.56

-0.71

< 0.0001

-1.3

-0.62

-2.02

-0.57

0.001

No

reference

Maternal blood lead (µg/dL)

-0.03

-0.38

-0.05

-0.01

0.001

0.03

0.36

-0.01

0.08

0.16

Umbilical cord blood lead (µg/dL)

-0.05

-0.43

-0.08

-0.02

< 0.0001

-0.03

-0.27

-0.09

0.02

0.26