Less common than acquired bleeding disorders in the perinatal period, congenital deficiencies of the clotting proteins, particularly the hemophilias A and B, can be just as devastating. Detection of these disorders may be delayed because a suspect family history is lacking in up to one third of the cases of hemophilia, and parents are usually asymptomatic in the other congenital factor deficiencies. Physiologically low levels of the liver-dependent and contact factors can make the interpretation of the common hemostasis screens difficult. Hence, the use of age-adjusted tables such as those presented here is essential. Congenital deficiencies of clotting proteins should be suspected when serious CNS bleeding occurs in an otherwise healthy baby generally after a day or two. Factor XIII or other less common factor deficiencies should be sought when there is prolonged bleeding from the umbilical stump. Bleeding after circumcision is a rare early indicator nowadays with better techniques. The availability of bedside ultrasound to detect CNS hemorrhage early and of fresh frozen plasma for treatment preceding the results of specific factor assays should prevent serious sequelae. Elective cesarean section is currently recommended when an unborn infant is known to have hemophilia.