Coagulation findings were examined in 55 cases of neonatal intracranial hemorrhages (ICH). Marked decreases of the platelet count, fibrinogen, factor XIII (F XIII) activity, were observed in these cases. However, the relatively mild increases in the alpha 2-plasmin inhibitor activity, alpha 2-plasmin inhibitor.plasmin complex and fibrin/fibrinogen degradation products level were observed and only about one third of the cases showed
abnormal values. In consideration of these coagulation findings, fifty-eight cases of premature infants were randomly divided into a treated group with a F XIII concentrate and a non-treated group. Thirty cases were administered within 6 hours after delivery to investigate the preventive effects against intraventricular hemorrhages (IVH). Compared in frequencies between both groups limited to the cases with a high risk of IVH, the frequency in the treated group was two out of 13 (15.4%), significantly low (p less than 0.05), while it was six out of eight cases (75.0%) in the non-treated group. From these results it was concluded that a F XIII concentrate is effective in the prophylaxis of IVH in premature infants.