Blood Group: Rh
Common: 15% of Caucasians, 8% of Blacks, and 1% of Asians are D- and at risk for developing anti-D.
Causes HDN: Yes
Critical Titer: 1:16
Anti-D accounts for 50% of all isoimmunization cases. Thankfully this has declined with the use of Rhogam (D immunoglobulin prophylaxis). Still, anti-D remains frequent and a cause of severe HDN. 
1 - https://www.ncbi.nlm.nih.gov/books/NBK2269/