Background: High maternal and child death with high fertility rate have been reported in Ethiopia. Extreme age at first birth is linked with both maternal and child morbidity and mortality. However, literatures showed there are limited studies on timing of first birth and its predictors in the area so far. Therefore, determining time to first birth and its predictors will help to design strategies to improve maternal and child survival.

Methods: A survey-based study was conducted among reproductive-age women in Ethiopia using Ethiopian demographic health survey (EDHS), 2016 data. Stratified two-stage cluster sampling technique was used for sampling. The Kaplan-Meier (KM) method was used to estimate time to first birth. Inverse Weibull gamma shared frailty model applied to model the data at 95% confidence interval (CI), adjusted hazard ratio (AHR) and median hazard ratio (MHR) were reported as effect size. Proportional hazard assumption checked using Schoenfeld residual test. Information Criteria was applied to select parsimonious model. Stratified analysis performed for interaction terms and statistical significance declared at p value<0.05.

Results: The overall median age at first birth found to be 20 years (IQR, 16-24years). The independent predictors of time to first birth were: marriage 15-17 years (AHR=2.33,95% CI:2.08-2.63),secondary education level (AHR=0.84,95% CI:0.78-0.96), higher education level (AHR=0.75, 95% CI:0.65-0.85), intercourse before 15 years in the married stratum (AHR=23.81, 95% CI:22.22-25.64), intercourse 15-17 years in married stratum (AHR=5.56, 95% CI:5.26-5.88),spousal age difference (AHR=1.11, 95% CI :1.05-1.16),and use of contraceptives (AHR=0.91, 95% CI [0.86-0.97]). The median increase in the hazard of early childbirth at a cluster with higher early childbirth is 16% (MHR=1.16, 95% CI [1.13-1.20]) than low risk clusters.

Conclusion:

In this study, first birth found to be at an early age. Early age at first marriage, at first sexual intercourse and their interaction terms, high spousal age difference, being Muslim were found to increase early motherhood. Conversely, living in most urban region, secondary and higher women education were identified to delay first birth. Investing on women education and protecting them from early marriage are required to optimize time to first birth. The contextual differences in time to first birth are a novel finding which requires more study and interventions.