Coagulation factors in the human fetus of about 20 weeks of gestational age.

In plasma samples of 11 fetuses of about 20 weeks of gestational age the following coagulation factors have been determined (mean values found are given in parentheses): fibrinogen (0.30 U/ml), prothrombin (+/-0.17 U/ml), factor V (0.28 U/ml), factor VII (0.21 U/ml), factor VIII coagulant activity (factor VIII:C) (0.12 U/ml), factor VIII-related antigen (factor VIIIR:Ag) (1.04 U/ml), coagulant factor VIII-related antigen (factor VII:CAg) (0.19 U/ml), factor IX coagulant activity (0.05 U/ml), factor IX antigen (less than or equal to 0.03 U/ml), factor X (0,19 U/ml) and antithrombin III (AT-III) (0.23 U/ml). Our data support the evidence that prenatal diagnosis of haemophilia A is at present possible; less optimism is warranted where haemophilia B is concerned. the number of samples is sufficient to establish normal values for the age group. Means of quality control of the sample-which is often difficult to obtain-are disscussed.