An investigation of maternal and neonatal platelet function.

We have previously shown that the human placenta possesses a potent platelet antiaggregatory activity which is probably due to an ADPase. This led us to investigate platelet aggregation (in response to: adenosine diphosphate; adrenaline; collagen) in maternal blood samples obtained pre- and post-delivery and in cord blood at the time of delivery. Platelet aggregation in maternal samples did not differ significantly pre- and post-delivery, nor did it differ significantly from platelet aggregation observed in age-matched, non-pregnant women. On the other hand, platelets obtained from cord blood samples were insensitive to adrenaline even when very high concentrations (100 mumol/l) of this agonist were used. This lack of response to adrenaline could be overcome by incubation of cord platelet rich plasma (PRP) with sub-aggregatory doses of collagen or ADP or by standing PRP at room temperature for 2-3 h. ADP-induced aggregation was also diminished in cord PRP samples but this was only significant at the lowest ADP concentrations. The physiological significance of these findings is unclear but it may be of relevance that plasma catecholamine levels are high in neonates. Some adults show a defect of aggregation with absence of response to adrenaline, suggesting that neonatal platelet function patterns may persist in some adults.