Modifications of erythrocyte aggregation during labor and delivery

Abstract

Pregnancy is associated with erythrocyte hyperaggregation which acutely returns to baseline during delivery, while a transient hyperviscosity syndrome induced by uterine contractions can be observed. We aimed at analyzing more precisely the modifications of erythrocyte aggregation during labor. 71 uterine contractions in 30 pregnant women (19–45 yr, mean 27.2 ± 9) were studied, with RBC aggregation (SEFAM erythroaggregometer) measured before, during and after the contraction. Aggregation indices at 10 and 60 sec progressively increased throghout labor (p<0.01). Partial and total dissociation thresholds progressively decrease during labor with a nadir (−10%) at delivery (p<0.01). The aggregation time is transiently shortened (p<0.01) during labor. Although previous measurements with the Myrenne aggregometer showed only during labor a return to nonpregnant values, this analysis by laser backscattering indicates that the stressful events which occur during uterine contractions increase the tendency of RBCs to form aggregates, although they disaggregate more easily.