Grand Rounds: Unmasking the many faces of maternal and fetal thrombocytopenia

September 1, 2006

Although most cases of mild-to-moderate maternal disease are caused by gestational thrombocytopenia and rarely cause problems, the OB is obliged to rule out more serious causes. And for far-less-common fetal disease, these experts help you differentiate the potentially life-threatening fetal alloimmune thrombocytopenia from a benign drop in platelet count.

At first, it seems like a routine delivery. You deliver what appears to be a perfectly healthy newborn, after a patient's uneventful pregnancy. But there's no way to predict severe fetal thrombocytopenia. During pregnancy-particularly a first pregnancy-there are not always advance warnings like the ecchymoses that develop after a birth and the newborn's ominously low platelet count. Suddenly, spontaneous intracranial bleeding is putting the infant at risk for brain damage or even death. What do you do when an aggressive approach is called for?

The good news is that gestational thrombocytopenia, found in roughly 5% of pregnancies (and usually beginning in the third trimester), doesn't typically cause maternal, fetal, or neonatal complications.1,2 Although the lower limit of normal platelet counts in pregnancy is considered to be 106 to 120×103/μL, it's well recognized that platelet counts can drop much lower, typically not below 70×103/μL. Gestational thrombocytopenia is mild, asymptomatic, and has only been linked to a history of thrombocytopenia in a previous pregnancy (recurrence risk is 18%). Routine obstetric management for the patient and fetus/newborn is recommended around the time of delivery, after which the disease resolves spontaneously.3 But a red flag should go up if a patient doesn't have these benign features. Then you must lose no time in aggressively seeking out other causes.