Thrombocytopenia is one of the two most common hematological problems in pregnant women. It is defined as the platelet (PLT) count below 150 × 103/μL. Gestational incidental thrombocytopenia (GIT) represents about 75% of thrombocytopenia cases in pregnancy and it is believed that GIT is secondary to accelerated platelet destruction and increased plasma volume associated with pregnancy. The pregnancy complications such as preeclampsia and its most severe form - HELLP syndrome account for 20% cases of thrombocytopenia in pregnancy and primary immune thrombocytopenic purpura (ITP) - for 3-4 percent. During ITP, maternal antiplatelet antibodies can pass through the placenta and bind to fetal thrombocytes leading to the development of fetal thrombocytopenia which occurs in about 50% cases. Even if the maternal platelet count stabilizes, the estimated fetal and neonatal risk of thrombocytopenia in ITP is approximately 30%. Other types of thrombocytopenia in pregnant women constitute 1-2% of cases (disseminated intravascular coagulation, autoimmunological diseases, congenital, infection and drug-related, concomitant with blood neoplastic diseases). Although thrombocytopenia in pregnant women usually has a mild course, in case of a significant decrease in PLT count may lead to dangerous bleeding, especially when the platelet count falls below 20 × 103/μL. Since it is important to identify the cause of thrombocytopenia and to determine the risk for both the mother and the child, this paper presents the influence of maternal thrombocytopenia on the pregnancy course as well as its etiology and diagnostics. The treatment principles are discussed.