A positive association between other inherited thrombophilias (homozygous 20210 prothrombin gene mutation and homozygous factor V Leiden) and IUGR of unknown cause was also found, P = .096, OR 6.106 (CI 95% 0.72–51.30), although it was not statistically significant (P = .096, OR = 6.106, CI 95% 0.72–51.30). This evidence concerns the gene F5 and Rare hereditary thrombophilia.