ITP in pregnancy and the newborn: introduction.

Idiopathic thrombocytopenic purpura (ITP) occurs more commonly in young women and is one of the commonest immune mediated disorders in pregnancy. It may exist as an incidental finding in an otherwise healthy pregnant woman or may be associated with symptomatic reduction in the platelet count and varying degrees of clinical hemorrhage. The condition termed incidental thrombocytopenia of pregnancy is invariably associated with a platelet count of greater than 100 x 10(9)/L and a very low incidence of fetal thrombocytopenia. Symptomatic thrombocytopenia is more commonly associated with low platelet counts in the fetus (estimated between 20%-40%). It has recently been suggested that the incidence of fetal thrombocytopenia is substantially lower than this figure. The management of ITP in pregnancy is complicated by the fact that fetal thrombocytopenia is difficult to diagnose and carries substantial risks during the delivery process with rare cases of fetal hemorrhage occurring spontaneously in utero. Unfortunately there are no laboratory studies that can be performed precisely in the mother that may predict the occurrence of fetal thrombocytopenia. Maternal management is usually directed towards treatment of maternal symptoms. Maternal treatment or response to treatment is inconsistently associated with predictable changes in the fetal platelet count. Obstetric management is aimed at reducing the risks of life threatening fetal hemorrhage occurring at the time of delivery, and fetal management is directed towards the obtaining of fetal platelet samples in order to plan an appropriate strategy for obstetrical delivery. Fetal blood samples are obtained either by a scalp vein puncture at the time of delivery or earlier in gestation by the use of the newer technique termed percutaneous umbilical blood sampling. Fetuses with platelet counts of less then 50 x 10(9)/L are generally delivered by cesarean section whereas those with counts greater than 50 x 10(9)/L are allowed to proceed with vaginal delivery assuming no obstetrical contraindications exist. The use of IVIgG therapy during pregnancy has theoretical implications on improving platelet counts in the mother in situations of severe hemorrhage, however cannot be considered to be appropriate treatment for the prevention of fetal thrombocytopenia, since the exogenous transport of IVIgG across the placenta appears to be inconsistent and unpredictable.(ABSTRACT TRUNCATED AT 400 WORDS)