The aim of the study is to investigate whether platelet activity is increased by hyperprolactinemia during pregnancy as reflected by beta-thromboglobulin level. Forty-eight healthy, pregnant, and 30 healthy, non-pregnant women were investigated with respect to platelet count, collagen/ADP and collagen/epinephrine closure times, beta-thromboglobulin and prolactin levels. The comparison of the variables between the two groups was made by Mann-Whitney U test. The correlation analyses were performed by Spearman's rank correlation test. Our results revealed that platelet counts, collagen/ADP and collagen/epinephrine closure times and beta-thromboglobulin showed no statistically significant differences between pregnant and non-pregnant women. We found no significant correlation between prolactin and collagen/ADP closure time (r=0.175), between prolactin and collagen/epinephrine closure time (r=-0.112) and between prolactin and beta-thromboglobulin (r=0.220) in pregnant women. Our findings suggest that platelet activity is comparable during pregnant and non-pregnant states and there is no significant effect of prolactin on platelet function in vivo as reflected by beta-thromboglobulin level.