Transfusion-associated fall in platelet count in very low birthweight infants.

Thirty-three infants with a birthweight of less than 1500 g were investigated retrospectively for the incidence and aetiology of thrombocytopenia occurring during the first week of life. The platelet count fell below 100 x 10(9)/l in 16 infants (48%). There was a moderately strong inverse correlation between the platelet count at its nadir during the first week or the first value below 100 x 10(9)/l and the percentage of blood volume transfused prior to this (r = -0.61; P less than 0.0001). When the platelet count was expressed as a percentage of the initial count the correlation was -0.74 (P less than 0.0001). The results were not affected by the elimination of the 10 infants with clinical conditions regarded as a probable cause of thrombocytopenia. The fitted least-squares regression line suggests that a transfusion equal to 10% of the blood volume on average reduced the platelet count by 19 x 10(9)/l or by 7% in these very low birthweight infants during the first week of life.