Thrombocytopenia in term infants: A population-based study

Objective: To assess the prevalence and causes of thrombocytopenia among fu ll-term infants. Methods: We conducted a 1-year, population-based surveillance study involvi ng all full-term infants (at least 37 weeks' gestation) born to native Finn ish women in Helsinki. In cases of thrombocytopenia (cord platelet count le ss than 150 x 10(9)/L) clinical risk factors were evaluated and immunologic studies were performed on both parents and on the infant; 95% confidence i ntervals (CIs) were calculated on the basis of binomial distribution. Results: platelet counts were done in cord blood from 4489 infants, 84.9% o f the study population. Eighty-nine infants had platelet counts below 150 x 10(9)/L (2.0%; 95% CI 1.5, 2.3) in cord blood and 11 were less than 50 x 1 0(9)/L (0.24%; 95% CI 0.10, 038). All causes of clinically important thromb ocytopenia, those presenting with bleeding and requiring treatment, were re lated to fetomaternal alloimmune thrombocytopenia. The incidence of severe alloimmune thrombocytopenia was one in 1500 live births and one in 900 of a ll thrombocytopenia. An immunologic mechanism was involved in ten of 65 (15 .4%; 95% CI 6.6, 24.2) infants studied and in four of 15 (26.7%; 95% CI 4.3 , 49.1) cases of severe thrombocytopenia. Conclusion: Immunologic studies should be considered in all cases of severe neonatal thrombocytopenia for careful monitoring and prevention of potenti ally severe complications in subsequent pregnancies. (Obstet Gynecol 2000;9 5: 441-6. (C) 2000 by The American College of Obstetricians and Gynecologis ts.).