Platelet values during normal pregnancy.

Blood samples were obtained from 26 healthy women at regular intervals throughout pregnancy and analysed using a Coulter Counter Model S Plus III. The mean values for the various haematological indices at each stage of gestation were first calculated; the platelet count showed a small decrease throughout pregnancy as did haemoglobin concentration while there was an apparent increase in mean platelet volume, platelet distribution width and white cell count. However, analysis of the trends within patients did not always reflect these mean changes; there was considerable variation in platelet count within individuals and the apparent fall in the group as a whole was accounted for by a considerable fall in a few individuals. The assumption that the trends in platelet values determined from groups of patients will indicate how individual pregnant women behave is misleading.