The platelets function of newborn aroused great interest in these last years. On this line, AA. made the stretching test according to Breddin K. and Burck K. H., and. Breddin's Aggregation test on blood coming from 30 couples mother-newborn, drawn immediately after the birth. 22 newborns (73.3%) showed a stretching less than 65%, as well as 21 mothers (70%). The average stretching of mothers resulted 59.5% (+/- 2.26), whereas the average of newborns resulted 55.03% (+/- 2.71). Student's T, calculated on these values, did not result statistically meaningfull. Data-difference of Aggregation test according to Breddin and Burck, pertinent the couples mother-newborn gave on contrary satisfactory statistical information (p less than 0.0001). The explanatory characteristics of stretching test did not allow further issues, whereas Aggregation test results allow to come to the conclusion that newborn's platelets show a less capacity, as to mother's platelets, to aggregata under a mechanical standardized stimulation.