The studies on the aetiological factors of a premature delivery constitute an old fear of obstetricians and epidemiologists. However, they remain confused and the very definition of prematurity is among the first sources of confusion. There are many therapeutic methods considered as preventive. Their efficacy is debatable whilst their secondary effects are obvious. In this article, the authors report the results of a retrospective study of observations of patients who presented threats of premature labour and analyzed the epidemiological aspects, the aetiological factors and the therapeutic methods. It seems important to consider the risk factors in order to prevent premature labour. A decrease in the use of betamimetics and an increase in that of therapies said to be of replacement does not seem to be accompanied by a relative increase in the incidence of prematurity.