Anti-D causes the most severe cases of HDFN. The pathophysiological events typically include:
- Anemia: Cord Hb can be less than 10 g/dL (100 g/L) and as low as 3-5 g/dL (30-50 g/L).
- Jaundice (icterus gravis): Jaundice occurs after delivery as fetal bilirubin is cleared by the mother during pregnancy. Extravascular fetal red cell destruction by maternal antibodies produces high bilirubin levels. The newborn, who is unable to produce adequate amounts of the liver enzyme glucuronyl transferase, is unable to conjugate the bilirubin into its water-soluble, excretable form.
- Kernicterus: If indirect bilirubin levels reach approximately 20 mg/dL (340 mmol/L), the fat-soluble unconjugated bilirubin deposits into the fat-rich brain cells, causing brain cell damage. Cerebral palsy, deafness, mental retardation, and other serious disorders can result.
- Hydrops fetalis: Gross edema occurs in severely affected infants, and often results in stillbirth or death soon after birth. Liver failure and hypoproteinemia also play a role in this syndrome.
- Enlarged organs: Liver, spleen, and heart
Laboratory findings include a positive direct antiglobulin test (DAT), low hemoglobin, increased reticulocyte count, and increased nucleated red blood cells.
