Rh incompatibility occurs when an Rh-negative pregnant patient carries an Rh-positive fetus, and fetal blood that enters the mother's circulation can trigger antibodies. In a later pregnancy these antibodies cross the placenta and destroy fetal red cells, causing anemia and hydrops.
Key symptoms
- Usually no symptoms in the pregnant patient
- Risk events: bleeding, trauma, miscarriage, procedures, birth
- Less fetal movement if the fetus is severely anemic
- Newborn jaundice or anemia after birth
What you find on exam
- Fundal height and fetal heart rate
- A large uterus or excess fluid can signal fetal hydrops
- Look for bleeding or trauma that could mix fetal and maternal blood
- Newborn: pallor, jaundice, swelling, enlarged liver
Tests
- Blood type, Rh and antibody screen at the first visit
- Antibody titer if sensitized
- Middle cerebral artery Doppler ultrasound to detect fetal anemia
- Kleihauer-Betke test after a large bleed or trauma to dose the immune globulin
Treatment basics
- Rh immune globulin at 28 weeks
- Rh immune globulin within 72 hours after birth of an Rh-positive baby
- Rh immune globulin after bleeding, trauma, pregnancy loss, ectopic pregnancy or procedures
- Sensitized patient: maternal-fetal medicine care and intrauterine transfusion for severe anemia
Red flags
- Positive antibody screen in an Rh-negative patient
- Signs of fetal anemia or hydrops on ultrasound
- Missed dose after a bleeding or trauma event
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.