Background: Short birth interval is a universal public health problem resulting in adverse fetal, neonatal, child and maternal outcomes. In Ethiopia, more than 50% of the overall inter birth spacing is short. However, prior scientific evidence on its determinants is limited and even then findings are inconsistent.
Methods: A community -based unmatched case-control study was employed on 218 cases and 436 controls. Cases were ever married reproductive age women whose last delivery has been in the past five years with birth interval of less than 3 years between the latest two successive live births whereas those women with birth interval of 3-5 years were taken as controls. A multistage sampling technique was employed on 30% of the kebeles in Dessie city administration. A pre-tested interviewer based questionnaire was used to collect data by 16 trained diploma nurses and 8 health extension workers supervised by 4 BSc nurses. The collected data were cleaned, coded and double entered into Epi-data version 4.2 and exported to SPSS version 22. Binary logistic regression model was considered and those variables with P<0.25 in the bivariable analysis were entered in to final model after which statistical significance was declared at P< 0.05 using adjusted odds ratio at 95% CI.
Result: In this study, contraceptive use (AOR = 11.2, 95% CI: 5.95-21.15), optimal breast feeding for at least 2 years (AOR = 0.098, 95% CI:0.047-0.208), age at first birth <25 years (AOR = 0.36, 95% CI: 0.282-0.761), having male preceding child (AOR = 0.46, 95% CI: 0.166-0.793) and knowing the duration of optimum birth interval correctly (AOR = 0.45, 95% CI: 0.245-0.811) were significant determinants of short birth interval.
Conclusion: Contraceptive use, duration of breast feeding, age at first birth, preceding child sex and correct understanding of the duration of birth interval were significant determinants of short birth interval. Fortunately, all these significant factors are likely modifiable. Thus, the existing efforts of optimizing birth interval should be enhanced through proper designation and implementation of different strategies on safe breastfeeding practice, modern contraceptive use and maternal awareness about the health merits of optimum birth interval.