Background: Birth interval has acquired importance in public health and family planning because of its implication for fertility, maternal, and child health. A short birth interval is associated with adverse perinatal, maternal, and infant outcomes. Moreover, too short birth interval lead to high fertility, which in turn contributes to accelerated population growth and undermines developmentefforts.This study aimed to assess the prevalence of short birth interval andits associated factors among married women who have at least two consecutive live births in Aroresa district, Sidaama Region, South East Ethiopia.

Method: - A community-based cross-sectional study was conductedfrom July 1/2023 to August 30/ 2023.The multistage sampling technique was used to select 608women who gave at least two live births. Data were collected by face-to-faceinterviewer questionnaires. Bivariate and multivariable binarylogistic regression analyses were executed.Model fitness and multicollinearity were checked. Statistically significant associations of outcome and independent variables were declared at a P-value of < 0.05.

Result: The prevalence of short birth interval was 47.5% (95%CI 43.7, 51.3) in the study area. Preceding child being female (AOR = 1.9, 95% CI: (1.32, 2.67)), non- user of contraceptive before conception of the last child (AOR=2.7, 95% (1.9, 3.9)), breastfeeding of the preceding child<24 months (AOR = 2, 95% CI (1.43, 2.9)) and preceding childbeingdead (AOR=2.6, 95% CI: (1.4, 4.9)).werestatistically significant with a short birth interval at a P-value<0.05.

Conclusion:This study found a higher prevalence of short birth intervals in the area compared to previous studies.Factors such as having a preceding female child, not using contraception, breastfeeding for less than 24 months, and having a deceased preceding child were significantly associated with short birth intervals. These factors pose challenges in achieving optimal birth spacing and impact maternal and child health outcomes.

Keywords: - Birth interval duration; Reproductive age women; maternal health; Child health