Defects of the middle line are an heterogeneous group of congenital malformations due to commune pathogenetic mechanisms. We have made a case-control study about 150 newborns, who have at least 1 defect of the middle line. Results prove an excess of males between the cases, due mostly to hypospadias. We haven't found families with defects of the middle line with x-linked manner of hereditary transmission. We haven't found any particular risk present in cases and not in controls. We haven't found any case with 2 or more middle line defects.