MTHFR and fetal growth restriction: A significant relationship between IUGR of unknown cause and PAI-1 and MTHFR gene mutation found in our study is in line with the results of the majority of other case-controlled studies which evaluated association of these conditions in general population of women with IUGR.[28,29] On the contrary, Said et al found no link between IUGR and PAI-1 and MTHFR gene mutations.[30] However, these discrepancies could be explained by huge differences regarding race and ethnicity between participants in conflicting studies.