In<unk>  maternal IgG antibodies (specific for platelet antigens) pass through the placenta and attack platelets in the fetal circulation.  This results in the fetus having low numbers of platelets and a tendency for the fetus or neonate to bruise and bleed.  Medical treatment is problematic.
Fetomaternal alloimmune thrombocytopenia
Neonatal alloimmune thrombocytopenia
Hereditary persistence of fetal hemoglobin
Platelet storage pool deficiency
Congenital protein C or S deficiency
Catastrophic antiphospholipid syndrome
Congenital amegakaryocytic thrombocytopenia
Protein S deficiency