Platelet reactivity in twin pregnancies.

BACKGROUND Gestational thrombocytopenia is more likely to occur in twin than singleton pregnancies. However, it is unclear whether platelets are more reactive in twin than singleton pregnancies. METHODS Changes in spontaneous platelet aggregation and concomitant fall in platelet count were examined over 90min after blood sampling in 171 and 52 citrated whole blood (CWB) samples from 59 and 17 women with singleton and twin pregnancies, respectively. Soluble P-selectin (sP-selectin) levels in the plasma were also determined. RESULTS CWB 60min after blood sampling during 2nd trimester exhibited significantly larger numbers of platelet aggregates (1297±1600 vs. 497±432/μl, P=0.040) concomitant with significantly greater net decrease in platelet count (152±55 vs. 115±45×10(9)/μl, P=0.036) in twin than singleton pregnancies, respectively. This was followed by significantly lower 3rd trimester platelet count (181±43 vs. 229±62×10(9)/l, P=0.009) with significantly greater mean platelet volume (8.0±1.2 vs. 7.1±1.1fl, P=0.021) in twin than singleton pregnancies, respectively. The 3rd trimester sP-selectin per platelet was significantly higher in twin than singleton pregnancies. CONCLUSIONS Platelets were more reactive in the 2nd trimester of twin than singleton pregnancies. This enhanced platelet reactivity may explain the decreased platelet count in the 3rd trimester of twin pregnancy.