The idiopathic thrombocytopenic purpura (ITP) associated to a pregnancy is a frequent eventuality, and this association have a high risk. The mother platelet numeration cannot predict the fetal affection, only the mother antiplatelet antibodies rate have a predictive value. The obstetrical attitude is highly discussed and is conditioned by the fetus platelet rate. If the corticotherapy brings an improvement of the maternal and fetal platelet rate, the gammaglobulin therapeutic interest will be confirmed. Thanks to a ITP case associated to pregnancy and a literature review, we will try to appreciate this disease for a pregnant woman, evaluate its consequences on the pregnancy and approach the different steps of the taking care actions.