Rh incompatibility

What is it?

Red blood cells carry markers on their surface. One of them is the Rh factor. If you have it you are Rh positive. If you do not, you are Rh negative. ¹

An Rh-negative person carrying an Rh-positive baby has a specific situation. Their immune system has never seen the Rh marker. If some of the baby's blood crosses into their circulation, which happens most often at delivery but also after bleeding, trauma or certain procedures, their immune system may treat it as foreign and make antibodies against it.

That process is called sensitization. It usually causes no problem in that pregnancy, because it takes time and the baby is already being born.

The problem is the next pregnancy. The antibodies are small enough to cross the placenta, and if that baby is also Rh positive, they attack the baby's red blood cells. ¹

The consequences for the baby range from mild anemia to severe anemia with heart failure before birth, and after birth to very rapid red cell breakdown that pushes bilirubin up fast. That is one of the routes to kernicterus. ²

Rh immune globulin prevents sensitization by clearing the baby's cells from the mother's circulation before her immune system responds to them. Once antibodies have formed, the injection no longer helps: it prevents, it does not reverse. That is why timing is everything. ¹

What does standard care look like?

Blood typing and antibody screening early in pregnancy. ¹

Rh immune globulin in the third trimester for Rh-negative people who are not already sensitized, at the timing guidance sets out. ¹

A dose after birth if the baby is Rh positive, given within the window guidance specifies. ¹

A dose after any event that can cause mixing of blood, including bleeding in pregnancy, abdominal trauma, amniocentesis, external cephalic version, miscarriage and ectopic pregnancy. ^{1 3}

Testing for the amount of fetal blood that crossed where a large bleed is suspected, so the dose can be adjusted.

Monitoring in a sensitized pregnancy, including antibody levels and Doppler study assessment of the baby's blood flow to detect anemia.

Newborn testing where the mother is Rh negative: the baby's blood type, a Coombs test test, blood count and bilirubin. ²

Records you can request. Your right of access under federal rules covers the record set your provider holds, including the prenatal record and every immune globulin dose. ⁴

What can go wrong?

Blood type not checked in early pregnancy. ¹

The third-trimester dose not given. ¹

No dose after delivery of an Rh-positive baby, or given outside the window. ¹

No dose after an event that warranted one, such as bleeding, trauma, version, amniocentesis or miscarriage. This is the most commonly missed situation, because these events happen outside routine visits. ¹

Antibody screening not repeated where indicated.

A sensitized pregnancy not monitored, so severe fetal anemia was not detected.

The newborn not tested where the mother is Rh negative, so rapidly rising bilirubin was not anticipated. ²

bilirubin not measured and treated against the thresholds in a baby with rapid red cell breakdown. ²

Whether any of this amounts to a departure from the standard takes a physician expert reading the whole record. Sensitization also occurs despite correct prophylaxis. ¹

Which injuries can follow?

• Kernicterus from very high bilirubin caused by rapid red cell breakdown. ²
• Dyskinetic cerebral palsy, the characteristic movement outcome of kernicterus. ⁵
• Hearing loss, which accompanies kernicterus. ⁶
• Severe anemia before birth, which in its most severe form causes heart failure in the baby.
• Neonatal seizures with severe bilirubin encephalopathy. ⁷
• Stillbirth in severe untreated cases. ¹
• Developmental delay following significant bilirubin brain injury, which is why developmental follow-up is arranged. ^{8 9}

Note that other blood group incompatibilities, particularly ABO, also cause newborn jaundice through the same mechanism of red cell breakdown, and they are not prevented by Rh immune globulin. ²

What does this look like in the records?

From the prenatal record

• Your blood type and Rh status, and the date it was determined. ¹
• Antibody screening results and dates.
• Every dose of Rh immune globulin, with the date and the indication.
• Any event during the pregnancy that should have triggered a dose: bleeding, trauma, procedures, version. ¹
• Records of any previous pregnancy, including whether a dose was given then.

From the delivery record

• The baby's blood type and Rh status.
• Whether a postpartum dose was given, and when. ¹

From the newborn record

• The Coombs test test result. ²
• Blood count and reticulocyte count.
• Every bilirubin value with the exact time and the baby's age in hours. ²
• Treatment given: phototherapy, immunoglobulin, exchange transfusion, and the times.

What can you do this week?

1. Request the complete labor and delivery record for you and your baby. The records request builder writes the letters for you.
2. Write down what you remember while it is fresh, using the delivery timeline builder.
3. Read how to read your labor and delivery records before the records arrive.
4. Check the deadline to file in your state with the statute of limitations lookup.