Background: There is controversy concerning the activation of blood platelets in newborns. According to some authors newborn platelets are hyporeactive and other authors indicate that they respond to agonist in a similar way as platelets in adults.Material/Methods: Forty seven newborns, 21 girls and 26 boys, were introduced to this study. PF4 (platelet factor 4) and BTG (beta – thromboglobulin) were determined in plasma from the umbilical artery.Results: The concentration of PF4 was higher in male newborns (89.55 IU/ml) than in female newborns (77.22 IU/ml). BTG level was also increased in male newborns 249.98 IU/ml, compared to female (218.76 IU/ml). The changes were statistically significant.Conclusions: Male newborns demonstrate more activated platelets than female newborns. The increased activation of newborn platelets may be related to the increased thrombinogenesis during delivery.

Keywords: activation, newborns, platelets, gender