ARTICLE Matrix metalloproteinases 1, 2, 3 and 9 functional single-nucleotide polymorphisms in idiopathic recurrent spontaneous abortion Nina Pereza a , Sas ˇ a Ostojic ́ a, * , Marija Volk b , Miljenko Kapovic ́ a , Borut Peterlin b a Department of Biology and Medical Genetics, Faculty of Medicine, University of Rijeka, B. Branchetta 20, 51000 Rijeka, Croatia; b Institute of Medical Genetics, Department of Gynaecology and Obstetrics, UMC Ljubljana, 1000 Ljubljana, Slovenia * Corresponding author. E-mail address: sasa@medri.hr (S Ostojic ́). Nina Pereza, MD, is a PhD student at the Faculty of Medicine, University of Rijeka. She works at the Department of Biology and Medical Genetics and her main interest of research is reproductive genetics, especially genetic causes associated with idiopathic recurrent spontaneous abortion. Abstract Idiopathic recurrent spontaneous abortion (IRSA) has been associated with abnormalities in the remodelling of endome- trial extracellular matrix, as well as aberrant matrix metalloproteinase (MMP) gene expression in endometrium of IRSA women and chorionic villi of IRSA concepti. This study investigated the association of five functional MMP gene promoter polymorphisms (MMP1 1607 1G/2G, MMP2 735 C/T, MMP2 1306 C/T, MMP3 1612 5A/6A and MMP9 1562 C/T) with IRSA. A total of 149 couples with at least three consecutive IRSA and 149 fertile couples were included in a case–control study. Genotype analysis was performed using PCR restriction fragment length polymorphism. Statistically significant differences were found in distributions of MMP2 735 CT (chi-squared 10.21, P = 0.006; OR 2.15, 95% CI 1.34–3.45, P = 0.001), and MMP9 1562 CC (chi-squared 9.06, P = 0.010; OR 2.21, 95% CI 1.30–3.80, P = 0.004) between IRSA women and controls. Combined analysis of MMP gene polymorphisms did not increase their predictive value. There were no statistically significant differences in genotype and allele frequencies of any polymorphism between IRSA men and controls. MMP2 735 C/T and MMP9 1562 C/T functional gene polymorphisms might be associated with an increased risk of IRSA in women.