Comparative evaluation of antepartum and postpartum platelet function in smokers and nonsmokers

Platelet aggregation was analyzed during normal pregnancy by evaluation of the same patient cohort (n = 19) on two separate prenatal visits and at 4 weeks post partum. To analyze platelet aggregation five different parameters were evaluated in platelet-rich plasma and whole blood (by impedance aggregometry) with the use of four different aggregating agents: adenosine diphosphate, collagen, sodium arachidonate, and epinephrine. Plasma levels of beta-thromboglobulin, thromboxane B2, and 1,6-keto-prostaglandin F1 alpha were also analyzed. Platelet counts rose 19% after delivery. Plasma levels of beta-thromboglobulin and thromboxane B2 were not significantly changed during the two antepartum visits, but B-thromboglobulin levels were modestly elevated post partum. Levels of 1,6-keto-prostaglandin F1 alpha decreased significantly from a mean of 125 pg/ml before delivery to 50 pg/ml post partum. All antepartum parameters on whole blood aggregation that were significantly different from postpartum values showed enhanced antepartum reactivity. In platelet-rich plasma, pregnancy was associated with greater platelet reactivity except for two variables, time to half-maximal aggregation for epinephrine and the extent of aggregation by collagen, both noted during the first antepartum evaluation. When the patient cohort of 19 was subdivided according to smoking status, all aggregation parameters of significance (p less than 0.05) demonstrated increased platelet reactivity during pregnancy compared with postpartum values. Smoking women accounted for a disproportionate number of significantly enhanced reactivity (seven variables versus three).