Data about the profile and risk factors of premature births in Tunisia are scarce. The objective of this study was to describe the epidemiological profile of preterm births in Monastir, Tunisia, and to study the chronological trends of associated factors over the years 1994–2012. A population-based study was conducted using data from the regional births database on all deliveries in public maternity units. The overall prevalence of preterm births among the 161 116 deliveries in the 19-year period was 5.60% (95% CI 5.13%–6.07%). The rate of preterm births and of adequate prenatal care increased significantly over the study period. Extremes of maternal age (≤ 19 and ≥ 35 years), having a twin pregnancy and the occurrence of complications during pregnancy were significant predictors of prematurity in the final regression model. Efforts should be made to improve the quality of health care in the region, especially for high-risk pregnancies.