AbstractPercutaneous umbilical blood sampling (PUBS), also called cordocentesis, is a newly introduced technique that enables blood samples to be obtained from the fetusin uterofor a variety of conditions. The major applications are for the diagnosis of fetal infections, karyotype analysis, fetal growth retardation, diagnosis of hematologic conditions, and metabolic evaluation. This procedure is gaining in popularity, since it provides direct information on fetal blood status. It can be applied to therapeutic manipulations such asin uterotransfusions or drug administration. The procedure is remarkably safe and has few technical problems. The applicability of its use in the assessment of fetal thrombocytopenia is also discussed in detail.