**Get emergency care right away if signs of a transfusion reaction start during or soon after a transfusion, and call your baby's doctor the same day if a newborn looks yellow in the first 24 hours or is feeding poorly.**
ABO incompatibility means red blood cells carry A or B markers that a person's immune system attacks. In transfusion, this is rare because blood is typed and cross-matched and your identity is checked at the bedside, but when it happens it can damage red cells quickly. In newborns, it usually shows up as jaundice in the first day or two when a mother with type O blood has a baby with type A or B, and most babies do well with feeding support, bilirubin checks, and phototherapy. Pregnancy itself is not treated for ABO incompatibility, though your prenatal team should know if an earlier baby needed phototherapy or an exchange transfusion. Speak up during any transfusion if you feel unwell, and keep newborn follow-up visits so bilirubin is tracked on schedule.
The warning signs to watch
Common questions
When should you see a doctor for ABO incompatibility?
ABO incompatibility needs urgent care in two situations. During or shortly after a transfusion, fever, chills, back or flank pain, dark or red urine, trouble breathing, or a sudden drop in blood pressure can signal a hemolytic reaction, so the transfusion is stopped and emergency care starts right away. In newborns, call the pediatrician the same day if jaundice appears in the first 24 hours, spreads to the arms or legs, or comes with poor feeding, few wet diapers, unusual sleepiness, or a high-pitched cry. Pregnancy itself does not require treatment for ABO incompatibility, but tell your prenatal team if an earlier baby needed phototherapy or an exchange transfusion.