Objective To assess the duration and severity of reactive thrombocytosis after caesarean section and vaginal delivery.
Design A prospective cohort study.
Setting A large teaching hospital.
Methods Women admitted for delivery at the Leicester Royal Infirmary were recruited into the study. The platelet count was measured before delivery and postnatally on days 3, 8, 12, 16, 20 and 24. Women who had antepartum haemorrhage, postpartum haemorrhage and those delivered by instrumental delivery were excluded from the study. Sixty-five were recruited, and 45 completed the study, 20 of whom were delivered by a normal vaginal delivery and 25 by caesarean section. A random effects model was used to compare platelet counts within and between the two groups to assess the severity and the timing of reactive thrombocytosis.
Results There were no statistically significant differences in booking and pre-delivery platelet counts between the two groups (mean values 248.4 × 109/L and 245 × 109/L in the normal vaginal group and 269.4 × 109/L and 251.6 × 109/L in the caesarean section group, respectively). Postnatally, a rise in the platelet count was noted in the normal vaginal delivery group, reaching statistically significant peak values, compared with booking and pre-delivery at days 8 and 12 of the postnatal period (mean value 365.8 × 109/L; P < 0.001 and 369.4 × 109/L; P < 0.001 respectively). In the caesarean section group, the platelet count was raised to a statistically significant high value, compared with booking and pre-delivery at day 8 of the postnatal period. The platelet count peaked at days 12 and 16 of the postnatal period (mean value 522.5 × 109/L; P < 0.0001 and 526.5 × 109/L; P < 0.0001, respectively) and remained significantly higher than booking and predelivery values for 24 days after the caesarean section. There was a greater rise in the platelet count in the caesarean section group compared with the vaginal delivery group. The platelet counts in the caesarean section group were significantly higher than these in the normal vaginal delivery group from day 12 to day 24 of the postnatal period.
Conclusion A significant rise in platelet count occurred eight to twelve days after normal vaginal delivery and caesarean section. The increase in platelet count continued to rise for 16 days after caesarean section, and it stayed significantly higher for more than 24 days after the delivery.