In the group with IUGR, 31.8% of patient were MTHFR homozygous, 45.5% MTHFR heterozygous, Prothrombin heterozygous and FV Leiden heterozygous 4.5% (coinheritance) and without thrombophilia 22.7%. The gene discussed is MTHFR; the disease is thrombophilia.