Thrombocytopenia in a newborn baby can be caused by –
Thrombocytopenia in neonate can be caused by

Isoimmune thrombocytopenia
Mothers with ITP (Autoimmune thrombocytopenia).
Mothers with antiphospholipid antibody (SLE).
Intrauterine infections with → Rubella, Syphilis, Toxoplasmosis, CMK HSV
Neonatal bacterial sepsis
Isoimmune thrombocytopenia
Autoimmune thrombocytopenia
SLE
All of these