Neonatal thrombocytopenia in the hypertensive disorders of pregnancy.

Infants of hypertensive mothers are at risk for a platelet count below 150 x 10(9)/L. To define this risk and assess maternal factors influencing the prevalence of neonatal thrombocytopenia, we collected cord blood samples from 520 infants of 607 consecutive hypertensive mothers with singleton pregnancies. The platelet count in cord blood from infants of hypertensive mothers was compared with that of a control normotensive population, and other comparisons were made among various maternal hypertensive groups. The rate of neonatal thrombocytopenia was 9.2% in hypertensive patients, compared with 2.2% in infants of normotensive mothers (P less than .00001). In the hypertensive group, preterm birth was the major risk factor for neonatal thrombocytopenia. Term infants of hypertensive mothers were no more likely to be thrombocytopenic than were control infants. Only two infants, both preterm, had cord platelet counts below 50 x 10(9)/L. Although obstetric interventions are not indicated, the rate of thrombocytopenia in preterm infants born to hypertensive women justifies neonatal scrutiny.