Maternal thrombocytopenia at term: a population-based study

Background. Thrombocytopenia is a common problem during pregnancy and often inappropriately managed. This study aimed to assess the prevalence and cau ses of maternal thrombocytopenia at term with special attention to immune m echanisms of thrombocytopenia and the need for assessing fetal risks. Methods. We conducted a 1-year population-based surveillance study involvin g 4382 fullterm (at least 37 weeks' gestation) women (83.8% of the study po pulation) and their infants from the city of Helsinki. Maternal and cord pl atelet counts were performed at delivery. Immune studies were performed if maternal platelet counts were less than 100x10(9)/l; 95% confidence interva ls (CIs) were calculated from the binomial distribution. Results. A total of 317 women (7.3%; 95% CI 6.5, 8.1) had platelet counts o f less than 150x10(9)/l. Most cases (81%) of maternal thrombocytopenia at t erm were due to gestational thrombocytopenia, which had no impact on either the mother or the fetus unless associated with some other medical or obste tric disorder. Other causes of thrombocytopenia were preeclampsia (16%) and idiopathic thrombocytopenic purpura (ITP) (3%). There was no association b etween maternal and fetal platelet counts: of the infants born to thrombocy topenic mothers, 2.1% had thrombocytopenia in the cord blood, which did not differ significantly from the 2.0% of thrombocytopenic infants born to non -thrombocytopenic mothers. Conclusion. Women with gestational thrombocytopenia do not require alterati on of their treatment. Fetal blood sampling is not considered necessary whe n thrombocytopenia is discovered unexpectedly at term.