Hi,
NAIT usually presents as petechiae in a well newborn, who then shows low platelet counts; usually quite profound, in 20-40,000. Mother's platelet count is normal with no h/o any auto-immune disorder. Subsequent tests from baby and both parents confirm NAIT with baby having anti-platelet antibodies, transferred across from mother (very similar to Rhesus disease).
If the baby's platelet counts respond to platelet transfusions, then I prefer not to give IVIG as later is a blood product pooled from multiple donars. NAIT is a self limiting disorder and baby's platelet counts improve after few weeks as long as we support that with platelet transfusions, there is no rush to expose the baby to a blood product from multiple donars.