Although thrombocytopenia is relatively rare in the general newborn population, it occurs frequently in patients admitted to newborn intensive care units. The major mechanisms are either increased destruction or decreased production of platelets. Multiple causes may be involved in some cases.
Thrombocytopenia in the newborn is reviewed here. Evaluation of a child with a bleeding disorder is discussed separately. (See "Approach to the child with bleeding symptoms".)
Historically, neonatal thrombocytopenia has been defined as a platelet count less than 150,000/microL based upon the definition used in adults, which corresponds to values at or below the 5th percentile. However, healthy preterm and term newborns have counts significantly below this level [1-3].
This was best illustrated from a study from the Intermountain Healthcare group that reviewed the platelet counts of 34,146 neonates (gestational age from 22 to 42 weeks) from the first three days of life . In neonates, the 5th percentile was lower than the standard adult value of 150,000/microL and decreased with decreasing gestational age. For example, the 5th percentile was 104,200/microL for infants below 32 weeks gestation and was 123,100/microL for late preterm (34 to 36 weeks gestation) and term infants (gestational age greater than 37 weeks). Platelet counts increased with advancing postnatal age.
Severe reductions (platelet count <50,000/microL) and/or persistent thrombocytopenia can result in bleeding. Severe and/or persistent thrombocytopenia requires evaluation, even in an asymptomatic infant.