Background Timing of postpartum family planning is crucial for maternal and child wellbeing by preventing unintended and closely spaced pregnancies. However, studies are limited on the time to use modern contraceptives in Ethiopia. Therefore, this study aimed to fill these gaps by assessing the time to initiate postpartum modern contraceptive and identifying its predictors among pregnant women in Ambo town, central Ethiopia.

Methods An institution based cross-sectional study was conducted among 356 pregnant women in Ambo town, Central Ethiopia. The data were analysed using STATA-16 software. Kaplan–Meier estimates were performed to explain time-to- modern contraceptive use. A Cox-proportional hazard regression analysis was conducted to identify predictors. The adjusted hazard ratio (AHR) with a 95% confidence interval was considered to declare a statistically significant association.

Results This study showed that the median survival time to initiate postpartum modern contraceptives was 6 months. In this study, the risk of modern contraceptive use was 2.13 times higher (AHR = 2.13; 95% CI: 1.02–4.45) among younger women, 1.44 times higher (AHR = 1.44; 95% CI: 1.09–2.66) among women with no desire for more children, and 2.25 times higher (AHR = 2.25; 95% CI: 1.02–4.95) among nulliparous women. However, it is 57% times lower (AHR = 0.57; 95% CI: 0.32–0.94) among pregnant women with current unintended pregnancy.

Conclusion and recommendation The median survival time to initiate postpartum modern contraceptive was 6 months. Age of the women, desire for more children, parity and pregnancy status were found to be the significant predictors of time to initiate postpartum modern contraceptive. Therefore health care providers and concerned stakeholders should consider these factors to increase the uptake of the postpartum contraceptive methods.