Objectives: The aim of this study is to investigate the association between gene mutations and preterm births and to determine whether these mutations are genetically risk factors for preterm birth, primarily to identify a + 331 G/A mutation of progesterone receptors in pregnant women that could be a genetic risk factor for preterm delivery. Study design: A retrospective study of pairs Participants and methods: 200 samples were analysed: 100 blood samples of which 50 blood samples were taken of pregnant women who gave birth prematurely and 50 blood samples of their children, as well as the same number of control samples of pregnant women and their children born in term. After venepuncture, the blood was subjected to DNA isolation and point mutation analysis on Real-Time PCR. Results: In this study, no statistically significant difference was found in the number of mutations between the test and control groups in both mothers and children, and the results of the Hi-square test were the same (χ2 = 0; Df = 1; p ˃ 0,99). In addition, preterm birth was not affected by the presence of a single +331 G/A mutation genotype at a given week of pregnancy (χ2 = 2,298; Df = 2; p = 0,32), and BMI (χ2 = 0; Df = 1; p ˃ 0,99) and the age of the pregnant woman (χ2 = 0,451; Df = 2; p = 0,79) are not risk factors for preterm delivery. It was also found that the decrease in progesterone concentration at the onset of birth is not significant (χ2 = 3,729; Df = 1; p = 0,05). Conclusion: The mutation of the + 331 G/A progesterone receptor does not represent a risk factor for preterm delivery.