The study data captured women between 11 and 41 years of age at first childbirth. The mean age at first birth was 20 years (SD=4). As shown in Table 2, of the 6,511 women who gave birth during the survey, 3,178 of the women experienced adolescent childbirth, accounting for 48.8% of all births.
Age: Almost half (47.1%) of the women who gave birth were aged 35-49 years. Of the mothers aged 35-49 years, approximately 40% had adolescent childbirth. The adolescent childbirth rate was highest (71%) among women aged 15-24 years.
First sexual debut: Approximately two-thirds (66.3%) of women had first sexual encounters outside unions, while 64% of women who had first sexual debut outside unions experienced adolescent childbearing. The adolescent birth rate was greater (52.6%) among women who had their first sexual experience within union than among those with encounters outside the union.
Abortion experience: Women who had never had abortion accounted for approximately three-quarters (74%) of all births, and most (76%) adolescent childbirths were found among women with no abortion experience. Women who had never terminated a pregnancy had markedly greater (50.3%) adolescent birth rates than women who had ever had an abortion.
Religion: Approximately 7 out of 10 (73.7%) women were Christians, while less than 10% of the women belonged to the traditional and other minority religious groups. Out of the small proportion of women who were traditional or other believers, 56.7% gave birth between the ages of 11-19 years, which was higher than Christian and Muslim women.
Marital status: Of the total women who were studied, 62% were married. Among unmarried women, more than half gave birth during adolescence which was higher than that of married women ((54.7% vs 45.2%).
Employment status: Women who were not working constituted a smaller proportion (16.5%) than those who were working. An elevated adolescent birth rate was observed among women who were not working compared with the working class (51.8% vs 48.2%).
Place of residence: Rural dwellers constitute a larger proportion (54.1%) of the study population and contribute approximately 61.9% of adolescent births. Notably, a heightened adolescent birth rate was identified among women from rural areas relative to urban dwellers (55.9% vs 40.5%).
Parity: The majority (60.7%) of the women had at least three births. A smaller proportion of mothers with one birth accounted for approximately 15% of adolescent childbirth; this represents an adolescent birth rate of 37.1% lower than women with two births (40.4%) and at least three births (55.3%).
Financial status: Among the study population, approximately 47% were poor, 21% were middle class and 33% were rich. In this research, the adolescent childbearing rate had an inverse relationship with the financial status of women. A higher childbirth rate was observed among poor women (56.4%) than among middle (53.9%) and rich women (34.8%).
Education: Secondary educated women had the largest proportion (43.9%). Moreover, women with postsecondary education had lower (8.5%) adolescent birth rates compared with other groups.
Table 2 Distribution of study characteristics across all women, adolescent birth and rates of adolescent birth
Variable
|
Category
|
All births
N=6511 (%)
|
Adolescent births
N=3178 (%)
|
Birth rate (Per 100)
|
Maternal age
|
15-24 years
|
979(15.0)
|
702 (22.1)
|
71.7
|
25-34 years
|
2,466 (37.9)
|
1,081(34.0)
|
43.8
|
≥ 35 years
|
3,066 (47.1)
|
1,395 (43.9)
|
45.5
|
First sexual debut
|
Outside union
|
4,314 (66.3)
|
2,023 (63.6)
|
46.9
|
Union
|
2,196 (33.7)
|
1,155 (36.4)
|
52.6
|
Abortion experience
|
No abortion
|
4,817 (74.0)
|
2,421 (76.2)
|
50.3
|
Had abortion
|
1,694 (26.0)
|
757 (23.8)
|
44.7
|
Religion
|
Traditional/other
|
448 (6.9)
|
254 (8.0)
|
56.7
|
Muslim
|
1,262 (19.4)
|
625 (19.7)
|
49.5
|
Christian
|
4,801 (73.7)
|
2,299 (72.3)
|
47.9
|
Marital status
|
Unmarried
|
2,471 (38.0)
|
1,351 (42.5)
|
54.7
|
Married
|
4,040 (62.0)
|
1,827 (57.5)
|
45.2
|
Employment status
|
Not working
|
1,075 (16.5)
|
557 (17.5)
|
51.8
|
Working
|
5,431 (83.5)
|
2,618 (82.5)
|
48.2
|
Place residence
|
Rural
|
3,522 (54.1)
|
1,968 (61.9)
|
55.9
|
Urban
|
2,989 (45.9)
|
1,210 (38.1)
|
40.5
|
Parity
|
One birth
|
1,303 (20.0)
|
483 (15.2)
|
37.1
|
2 births
|
1,254 (19.3)
|
507 (16.0)
|
40.4
|
At least 3 births
|
3,954 (60.7)
|
2,188 (68.8)
|
55.3
|
Financial status
|
Poor
|
3,029 (46.5)
|
1,707 (53.7)
|
56.4
|
Middle
|
1,365 (21.0)
|
735 (23.1)
|
53.9
|
Rich
|
2,117 (32.5)
|
736 (23.2)
|
34.8
|
Education
|
No education
|
2,125 (32.6)
|
1,167 (36.7)
|
54.9
|
Primary
|
1,282 (19.7)
|
777 (24.4)
|
60.6
|
Secondary
|
2,857 (43.9)
|
1,213 (38.2)
|
42.5
|
Higher
|
247 (3.8)
|
21 (0.7)
|
8.5
|
N, frequency; %, percentage
Kaplan-Meier survivor function curves
Figure 1 displays a plot that compares the survival experience of women who reported working and those who were not working. Based on the follow-up time in each of the two groups, it appears that women who were not working had shorter survival times. Furthermore, the log-rank test for equality of survivor functions found a p-value of 0.05, indicating a statistically significant difference between the two groups. This implies that women who are not working are associated with higher adolescent childbirths than those working.
Figure 2 displays the survival function for a place of residence. The graph suggests that women in rural areas have shorter survival times when compared with urban dwellers, indicating that rural women are at a higher risk of adolescent childbirth before their twentieth birthday than urban women. To confirm this, the log-rank test was conducted, and a statistically significant difference between urban and rural survival functions was detected (p-value <0.001).
Figure 3 shows the Kaplan-Meier survivor functions for financial status. The graph depicts a lower cumulative survival probability among poor women when compared with middle and rich women. This indicates that rich women had a lower risk of adolescent childbearing than middle and poor women. This assertion was supported by a log-rank test for equality of survivor functions that observed a statistically significant difference (p-value < 0.001).
Figure 4 displays a graph that compares the survival experience of women based on the education level. From the follow-up time in each of the four groups, it appears that women who have secondary and higher have longer survival times relative to those with primary and no education. This implies that women with at least secondary education were at lower risk of having a child before attaining 20 years when compared with their counterparts who had primary or no formal education. Furthermore, the log-rank test for equality of survivor functions found a p-value of <0.001, indicating a statistically significant difference between the four groups.
Hazard model results
Some risk factors violated the proportional hazard assumption that their hazard functions would remain proportional and constant over time. The study variables first sexual debut (p-value=0.018), maternal age (p-value= 0.014), marital status (p-value=0.001), and parity (p-value< 0.001) violated the proportional hazard assumption with a significant association in the Schoenfeld residuals test and hence were not considered in the univariate model. Furthermore, the coefficients from the positive and negative correlations were compared. The sensitivity analyses observed no significant difference in the parameter estimates, indicating that the independent censoring assumption was not violated.
As shown in Table 3, all the study predictors that were considered in the unadjusted model to explore the hazard of having adolescent childbirth had a p-value less than 0.2, and no multicollinearity was detected among the variables evidenced by VIF less than 4 and tolerance of more than 0.2. Moreover, all the selected risk factors were included in the multivariable model. No confounding and significant interaction terms were detected in the multivariable model. The final model had a smaller AIC of 7,226.5 than the null model (without predictors) with AIC of 7,871.0 and hence was considered a better model fit.
The adjusted hazard ratios reported in Table 3 demonstrate that the significant effects of first sexual debut, religion and abortion experience on the adolescent childbirth in the unadjusted model were attenuated after controlling for all other risk factors.
Employment status: The hazard of adolescent childbearing among women who were not working was 17% (95% CI= 1.07 to 1.29) higher than those who were working.
Place residence: The analysis revealed that women in rural areas were 22% (95% CI= 1.09 to 1.37) more likely to experience adolescent childbirth when compared with urban dwellers.
Financial status: The likelihood of having adolescent childbirth among poor and middle-class women was 71% (95% CI= 1.49 to 1.95) and 67% (95% CI= 1.48 to 1.88) respectively, greater than that among rich women.
Education: Secondary and higher educated women were 74% (95% CI= 0.67 to 0.82) and 10% (95% CI= 0.06 to 0.16) respectively, less likely to give birth during adolescence than women with no education. However, women with primary education were 25% (95% CI= 1.14 to 1.38) more likely to have adolescent childbirth than uneducated women.
Community effect: The estimated variance of the gamma frailty distribution of 0.08 was significant (LRT ᵪ2 = 54.60, p<0.001) suggesting that some communities had greater hazards of adolescent childbirth than other communities. Furthermore, the computed variance describes the unexplained heterogeneity at the community level.
Table 3 Unadjusted and adjusted hazard ratio (HR), and 95% confidence interval (CI) of Cox proportional hazards models predicting adolescent births
Variable
|
Category
|
Unadjusted
|
Adjusted
|
HR (95% CI)
|
P-value
|
HR (95% CI)
|
Abortion experience
|
No abortion
|
Reference
|
< 0.001
|
-
|
Had abortion
|
0.83 (0.76, 0.89)
|
-
|
Religion
|
Traditional/other
|
Reference
|
< 0.001
|
-
|
Muslim
|
0.80 (0.69, 0.93)
|
-
|
Christian
|
0.71(0.62, 0.81)
|
-
|
Employment status
|
Working
|
Reference
|
0.003
|
Reference
|
Not working
|
1.15 (1.05, 1.26)
|
1.17 (1.07, 1.29)
|
Place residence
|
Urban
|
Reference
|
< 0.001
|
Reference
|
Rural
|
1.91 (1.78, 2.05)
|
1.22 (1.09,1.37)
|
Financial status
|
Rich
|
Reference
|
< 0.001
|
Reference
|
Middle
|
2.28 (2.06, 2.53)
|
1.67 (1.48,1.88)
|
Poor
|
2.66 (2.43, 2.90)
|
1.71 (1.49,1.95)
|
Education
|
Higher
|
Reference
|
< 0.001
|
Reference
|
Secondary
|
0.06 (0.07, 0.17)
|
0.10 (0.06, 0.16)
|
Primary
|
0 .58 (0.54. 0.63)
|
0.74 (0.67, 0.82)
|
No education
|
1.18 (1.08, 1.29)
|
1.25 (1.14, 1.38)
|
Community Frailty
|
Variance (SE)
|
-
|
-
|
0.081 (0.015)
|
CI, confidence interval; HR, hazard ratio; %, percentage; SE, standard error