Background Low-dose aspirin (LDA) is recommended to improve birth outcomes in high-risk pregnant women from developing countries. There is no aggregate data from developing countries on LDA’s effect on preterm births. Objective To systematically review and collate clinical data to determine the effects of LDA on preterm births in women from low- and middle-income countries (LMICs). Search strategy MEDLINE, Embase and Cochrane CENTRAL databases were systematically searched in 2020. Selection criteria Randomized Controlled Trials (RCTs) of LDA compared with placebo or no treatment for preterm births in at-risk pregnant women from LMICs. Data collection and analysis Two authors independently screened the studies, extracted data and assessed quality. Pooled effect sizes were calculated using random effects models. The Cochrane risk of bias and Grading of Recommendations Assessment, Development and Evaluation (GRADE) tools were used to assess the quality of studies and overall quality of evidence. Main results Ten RCTs with 23 654 participants were included; studies were published between 1996 and 2020. Nine RCTs with 23 486 patients were pooled for the outcome preterm birth. Meta-analysis results suggest significantly reduced risks of preterm births (RR 0.90, 95% CI 0.82-0.98, p = 0.01) and perinatal mortality (RR 0.83, 95% CI 0.73-0.94, p < 0.01) in the LDA group. Conclusion Targeted LDA therapy should be considered to reduce preterm births in at-risk pregnant women from LMICs. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Keywords Low-dose aspirin, preterm birth, pre-eclampsia