Reacting appropriately to thrombocytopenia in pregnancy.

: The lower limit of normal for the platelet count is considered to be 150,000/cu mm in both pregnant and nonpregnant normal adults. In the absence of preeclampsia, sepsis, drugs, or other apparent causes, the finding of asymptomatic mild thrombocytopenia in pregnant women is compatible with previously unrecognized immune thrombocytopenic purpura (ITP). Because of the risk of fetal/neonatal thrombocytopenia and the subsequent risk of neonatal intracranial hemorrhage in infants born of mothers with ITP, the optimal mode of delivery for an asymptomatic but thrombocytopenic mother is problematic. Conceivably, those gravidas with mild previously unrecognized thrombocytopenia may not have ITP and thus could be spared cesarean section. From the platelet counts of 730 antepartum patients, we found a mean value of 263,900/cu mm with a standard deviation of 66,000/cu mm, yielding 95% confidence limits of 134,500 to 393,300/cu mm. The distribution is statistically indistinguishable from a normal distribution. Of 26 asymptomatic thrombocytopenic patients with no hematologic history, none had infants with hemorrhage or platelet counts less than 100,000/cu mm. Only one patient subsequently had severe glucocorticoid-resistant thrombocytopenia requiring splenectomy several months after delivery. The remaining patients continue to be asymptomatic to date, with platelet counts greater than 100,000/cu mm. We suggest a plan for managing less than normal platelet counts in asymptomatic gravidas without a history of hematologic abnormality.