Platelet reactivity changes significantly throughout all trimesters of pregnancy compared with the nonpregnant state: a prospective study

Abstract

Objective Platelets play an important role in the pathophysiology of uteroplacental disease and platelet reactivity may be an important marker of uteroplacental disease activity. However, platelet reactivity has not been evaluated comprehensively in normal pregnancy. We sought to evaluate platelet reactivity using a number of agonists at defined time points in pregnancy using a novel platelet assay and compare these with a nonpregnant cohort.Design Prospective longitudinal study.Setting Outpatient department of a large tertiary referral centre.Sample Eighty participants with 30 nonpregnant women and 50 pregnant women assessed longitudinally.Methods This was a prospective cohort study performed longitudinally throughout uncomplicated singleton pregnancies with participants recruited before 15 weeks of gestation. They were controlled for a number of factors known to affect platelet reactivity. Blood samples were obtained in each trimester. Thirty nonpregnant healthy female volunteers also had a platelet assay performed. A modification of standard light transmission aggregometry was used to assess platelet function, with light absorbance measured following the addition of five different agonists at submaximal concentrations. Dose-response curves were plotted for each agonist for the nonpregnant cohort and in each trimester for the pregnant cohort.Main outcome measures Dose-response curves and median effective concentration.Results When compared with the nonpregnant controls a significant reduction was demonstrated in platelet reactivity to collagen during the first trimester of pregnancy (P < 0.0001). Platelet aggregation increased significantly from the first to third trimesters in response to collagen and arachidonic acid.Conclusion Platelet reactivity varies according to pregnancy state, gestational age and agonist. The finding that platelet reactivity is reduced in the first trimester of pregnancy may be useful for the interpretation of further studies examining the role of platelet reactivity in the first trimester of pregnancies that develop uteroplacental disease.

Platelet aggregation in citrated whole blood of the first trimester of pregnancy

“…Based on these reports [20][21][22], the significant positive correlation between MPV and number of PA observed in this study implied that PA count in our system may have reflected platelet reactivity. Therefore, the consistently lower PA count in addition to lower degree of fall in platelet count in the blood of pregnant women than in non-pregnant women in this study strongly suggested that platelet reactivity is reduced in early pregnancy, consistent with results of the previous study by Burke et al [19].…”

“…These reports led to the misunderstanding that platelet reactivity in early pregnancy is similar to that in non-pregnant women, but increases gradually with advancing gestation, especially in women complicated with HDP. Therefore, the results of the study of Burke et al [19] indicating reduced platelet reactivity in early pregnancy was surprising. Burke et al [19] reported that collagen-induced platelet aggregation was lowest during the first trimester, increased in the second and third trimesters and became comparable to that in non-pregnant women.…”

“…Therefore, the results of the study of Burke et al [19] indicating reduced platelet reactivity in early pregnancy was surprising. Burke et al [19] reported that collagen-induced platelet aggregation was lowest during the first trimester, increased in the second and third trimesters and became comparable to that in non-pregnant women.…”

“…However, previous studies examining platelet activation during normal pregnancy yielded conflicting results-some reported increased activation [13,15,16], while others reported no change [17,18]. In addition, a recent report suggested that platelet reactivity to collagen was significantly reduced during the first trimester of pregnancy compared with that in non-pregnant controls [19].…”

Platelet reactivity in twin pregnancies

“…The increase in PA counts in CWB was lowest during the 1 st trimester and greatest approximately 1 month postpartum in both singleton and twin pregnancies, consistent with the results of recent studies [18,28]. Collagen-induced platelet aggregation is significantly reduced in the 1 st trimester of pregnancy compared to non-pregnant women [28].…”