When should you see a doctor for ABO incompatibility?
Last updated September 6, 2026.
**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.
What to do
- Call 911 for reaction signs: Chills, fever, flank pain, dark urine, or breathing trouble during a transfusion is an emergency, and the transfusion should be stopped first.
- Speak up at the bedside: Confirm staff check your name and armband against the blood bag label before the transfusion starts.
- Watch a newborn's color and feeding: Yellow skin in the first 24 hours, poor feeding, or fewer wet diapers than expected means a same-day call to the pediatrician.
- Keep the bilirubin follow-up: Babies discharged early often need a recheck within one to two days, so do not skip that visit.
- Share your history: Tell your prenatal team about any prior newborn who needed phototherapy or an exchange transfusion.
- Know your blood type: Keep your blood type and any past transfusion reaction in your health record so future care teams see it.
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