These anti-Rh positive antibodies move through the placenta into the fetus where they destroy the fetus' circulating red blood cells. First-born infants are often not affected as it takes time for the mother to develop antibodies against the fetal blood. Rh incompatibility may cause symptoms ranging from very mild to death of the newborn. Hemoglobin is converted into bilirubin , which causes an infant to become jaundiced. The jaundice of Rh incompatibility may range from mild to very high levels.
Hydrops fetalis often results in death of the infant shortly before or after delivery.
Kernicterus is a neurological syndrome caused by deposition of bilirubin into CNS tissues that develops in extremely jaundiced infants, especially those with severe Rh incompatibility. Later a high-pitched shrill cry may develop along with unusual posturing, a bulging fontanelle, and seizures . Infants may die suddenly of kernicterus. If they survive they later develop decreased muscle tone , movement disorders, high-pitched hearing loss , seizures, and decreased mental ability. Rh incompatibility develops only when the mother is Rh negative and the infant is Rh positive.