Table 5 Crude and adjusted hazard ratios of time to second birth interval among women in selected four SSA countries

Fertility desired

No more (R)

1

1

1

Wanted

0.96 (0.94,0.98)***

0.93 (0.92,0.95)***

0.86 (0.85,0.88)***

Undecided

1.04 (1.00,1.08)

1.00 (0.96,1.04)

0.92 (0.89,0.96)***

Contraceptive use

Never

1.34 (1.31,1.37)***

1.35 (1.32,1.38)***

0.93 (0.90,0.95)***

Formal

1.07 (1.04,1.10)***

1.07 (1.04,1.10)***

0.93 (0.90,0.95)***

Current (R)

1

1

1

Country

Nigeria

2.50 (2.42,2.59)***

1.85 (1.78,1.93)***

Ethiopia

1.47 (1.42,1.53)***

0.99 (0.95,1.04)

DR Congo

2.64 (2.54,2.73)***

2.01 (1.93,2.10)***

South Africa (R)

1

1

Residence

Urban (R)

1

1

Rural

1.35 (1.32,1.37)***

1.10 (1.07,1.13)***

Age at birth

 < 20 (R)

1

1

20–24

0.89 (0.87,0.90)***

0.98 (0.96,1.00)*

 ≥ 25

0.77 (0.75,0.79)***

0.87 (0.84,0.90)***

Wealth index

Low (R)

1

1

Middle

0.92 (0.90,0.94)***

0.96 (0.94,0.99)**

High

0.70 (0.69,0.72)***

0.86 (0.83,0.88)***

Education

No education (R)

1

1

Primary

0.81 (0.79,0.82)***

0.84 (0.82,0.86)***

Secondary

0.65 (0.64,0.67)***

0.81 (0.79,0.83)***

Higher

0.56 (0.54,0.59)***

0.75 (0.72,0.79)***

Employment status

Not working (R)

1

1

Working

1.12 (1.10,1.14)***

0.91 (0.90,0.93)***

Marital at FB

Never married (R)

1

1

Married before FB

2.87 (2.74,3.00)***

2.13 (2.03,2.24)***

Married after FB

2.25 (2.14,2.36)***

1.84 (1.75,1.93)***

FB sex

Male

1

1

Female (R)

1.02 (1.00,1.04)

1.01 (0.99,1.03)

FB survival

Dead

1.15 (1.10,1.19)***

1.06 (1.02,1.09)**

Alive (R)

1

1

Deviance (-2ll)

971,933.6***

964,037.4***