Table 5 The multivariable data analysis result in the final Weibull AFT model

place of residence(Ref. = rural)

 Urban

-0.06

0.94

[0.92,0.96]

0.009

0.000*

women age(Ref. = 15–19)

 19–24

0.03

1.03

[0.95,1.11]

0.039

0.415

 25–29

0.06

1.06

[1.03,1.09]

0.017

0.000*

 30–34

0.02

1.02

[1.01,1.04]

0.012

0.013*

 35–39

0.03

1.03

[1.01,1.05]

0.011

0.007*

 40–44

0.003

1.01

[1.01,1.03]

0.011

0.001*

women education(Ref. = educated women)

 Non-educated

0.03

1.03

[1.00,1.06]

0.013

0.018*

 Primary educated

0.13

1.14

[1.12,1.16]

0.011

0.000*

wealth index(Ref. = poor)

 Middle

-0.01

0.99

[0.97,1.01]

0.012

0.400

 rich

-0.06

0.94

[0.92,0.96]

0.009

0.000*

Sex of child(Ref. = male)

 female

-0.02

0.98

[0.96,1.00]

0.009

0.057

Smoking status(Ref. = Nonsmoker)

 Smoker

0.47

1.60

[1.57,1.63]

0.015

0.000*

 age of child

-0.01

0.99

[0.89,0.99]

0.001

0.000*

Birth interval(Ref. = 2-3 years)

  < 2 year

0.02

1.02

[0.99,1.04]

0.014

0.057

  > 4 year

0.01

1.01

[100,1.02]

0.006

0.000*