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Table 4 Factors associated with time to second birth interval among women in Nigeria and South Africa

From: A comparative analysis of the influence of contraceptive use and fertility desire on the duration of second birth interval in four sub-Saharan African countries

Characteristic

Nigeria

South Africa

Crude model

Model 1

Model 2

Crude model

Model 1

Model 2

HR (95% CI)

aHR (95% CI)

aHR (95% CI)

HR (95% CI)

aHR (95% CI)

aHR (95% CI)

Fertility desired

No more (R)

1

1

1

1

1

1

Wanted

1.02(0.99,1.05)

1.02(0.99,1.05)

1.00(0.97,1.03)

0.50(0.46,0.54)c

0.51(0.47,0.55)c

0.51(0.47,0.55)c

Undecided

1.07(1.01,1.12)a

1.07(1.01,1.12)a

1.03(0.98,1.08)

0.73(0.62,0.84)c

0.76(0.65,0.88)c

0.74(0.64,0.86)c

Contraceptive use

Never

0.97(0.93,1.00)

0.96(0.93,1.00)a

0.80(0.77,0.83)c

0.75(0.69,0.81)c

0.77(0.71,0.83)c

0.76(0.70,0.82)c

Formal

0.88(0.84,0.92)c

0.88(0.84,0.92)c

0.84(0.81,0.88)c

0.85(0.79,0.92)c

0.91(0.84,0.98)a

0.90(0.83,0.97)b

Current (R)

1

1

1

1

1

1

Ethnicity

Hausa (R)

1

 

1

   

Igbo

0.78(0.75,0.81)c

 

1.06(1.00,1.13)a

   

Yoruba

0.62(0.60,0.65)c

 

0.77(0.73,0.81)c

   

Don’t know/others

0.73(0.71,0.75)c

 

0.89(0.85,0.92)c

   

Black/African (R)

   

1

 

1

White

   

1.45(1.19,1.76)c

 

1.53(1.24,1.88)c

Coloured

   

0.99(0.89,1.10)

 

1.05(0.94,1.17)

Indian/Asian/other

   

1.00(0.74,1.36)

 

1.09(0.80,1.49)

Residence

Urban (R)

1

 

1

1

 

1

Rural

1.16(1.13,1.19)c

 

1.05(1.02,1.09)b

1.27(1.19,1.35)c

 

1.16(1.07,1.24)c

Religion

Christianity (R)

1

 

1

   

Islam

1.37(1.33,1.40)c

 

1.22(1.17,1.27)c

   

Traditionalist/other

1.17(1.03,1.34)a

 

1.31(1.14,1.49)c

   

Age at FB

 < 20 (R)

1

 

1

1

 

1

20–24

0.92(0.89,0.95)c

 

1.02(0.99,1.05)

0.99(0.92,1.06)

 

1.02(0.96,1.10)

 ≥ 25

0.83(0.80,0.87)c

 

0.98(0.94,1.02)

0.80(0.72,0.88)c

 

0.88(0.79,0.98)a

Wealth index

Low (R)

1

 

1

1

 

1

Middle

0.86(0.83,0.88)c

 

0.95(0.92,0.98)b

0.87(0.81,0.94)c

 

0.92(0.86,1.00)a

High

0.73(0.71,0.75)c

 

0.87(0.83,0.90)c

0.71(0.66,0.77)c

 

0.75(0.68,0.83)c

Education

No education (R)

1

 

1

1

 

1

Primary

0.81(0.79,0.84)c

 

0.97(0.93,1.01)

0.97(0.81,1.17)

 

0.96(0.79,1.15)

Secondary

0.75(0.73,0.77)c

 

0.99(0.95,1.03)

0.74(0.63,0.88)b

 

0.86(0.72,1.02)

Higher

0.69(0.66,0.72)c

 

0.93(0.87,0.99)a

0.67(0.55,0.81)c

 

0.88(0.71,1.08)

Employment

Not working (R)

1

 

1

1

 

1

Working

0.85(0.82,0.87) c

 

0.95(0.92,0.98)b

0.85(0.79,0.90)c

 

0.85(0.79,0.90)c

Marital at FB

Never married (R)

1

 

1

1

 

1

Married before FB

3.67(3.27,4.12)c

 

3.26(2.90,3.66)c

1.63(1.51,1.77)c

 

1.57(1.45,1.70)c

Married after FB

3.02(2.68,3.41)c

 

2.87(2.55,3.24)c

1.30(1.21,1.39)c

 

1.32(1.23,1.42)c

FB sex

Male (R)

1

  

1

  

Female

1.00(0.97,1.02)

  

1.00(0.94,1.07)

  

FB survival

Dead

1.13(1.07,1.19)c

 

1.11(1.05,1.16)c

0.94(0.80,1.11)

  

Alive (R)

1

 

1

1

  

Deviance (-2ll)

 

458,619.0c

456,902.2c

 

62,423.8c

62,116.4c

  1. cp < .001; bp < .01, ap < .05; (a)HR—(adjusted) hazard ratio; CI–confidence interval; R—reference category; ll—loglikelihood; FB—first birth