HYPOTHESIS: PROGINS alu insertion in the progesterone receptor gene is a genetic risk factor for preterm delivery. OBJECTIVES: The objectives of this study were to investigate the association of gene mutation in the progesterone receptor (PROGINS alu insertion) with the occurrence of spontaneous preterm birth and to determine whether the mutation is a genetic risk factor for preterm delivery. STUDY DESIGN: Retrospective study. PARTICIPANTS AND METHODS: The study population in this study is a maternity ward from the Clinic for Gynecology and Obstetrics, Clinical Hospital Center Osijek. The study population of pregnant women who gave birth prematurely consists of 100 samples (50 women giving birth, 50 newborns). The control group (50 women giving birth, 50 newborns) consists of term pregnant women who have given birth spontaneously. Exclusion criteria are iatrogenic preterm delivery (induction for preeclampsia, diabetes and more). The blood of pregnant women was sampled by venipuncture, and the blood of newborns was obtained from the umbilical cord. DNA was isolated from whole blood by commercial spin columns and the existence of PROGINS alu insertion was examined using PCR and electrophoresis. The results were statistically analyzed. RESULTS: Each sample was assigned a corresponding genotype. After the statistical analysis, it was found that there was no significant difference in the frequency of PROGINS alu insertion between the subjects and the control group.Comparison of maternity control and respondent groups (p = 0.8456); comparison of children from the control group and children of the subjects (p = 0.558). Tests that were used are Chi-squared test, Student t-test and Mann-Whitney U test for independent samples. The significance level was set at p = 0.05. CONCLUSION: From the aforementioned research results we can conclude that PROGINS alu insertion in the progesterone receptor gene is not a genetic risk factor for preterm delivery.