AN INFANT weighing 3.5 kg was born at term by spontaneous vaginal delivery with rupture of membranes occurring 10 hours prior to delivery and light meconium staining of the amniotic fluid. The pregnancy had been unremarkable with good prenatal care. Apgar scores were 9 at 1 and 5 minutes. The infant developed multiple petechiae at 9 hours of age. A hematologic workup was remarkable for a white blood cell count of 21 000×106/L with a normal differential cell count and a platelet count of 32 000×109/L. Maternal platelet count the same day was 253 000×109/L. Blood samples for culturing were obtained. The infant was treated with ampicillin sodium and gentamicin sulfate and transferred for further evaluation of thrombocytopenia.
The physical examination revealed a well-appearing, full-term newborn with multiple petechiae over the body and moderate bruising over the scalp. The fontanelle was normal. There were