Blood group incompatibility (rhesus disease)
Maternal anti-D against RhD-positive fetus
Overview
Haemolytic disease of the fetus/newborn from maternal IgG antibodies (classically anti-D) crossing the placenta to destroy fetal red cells. Prevented by routine anti-D prophylaxis in rhesus-negative women; causes fetal anaemia/hydrops and neonatal jaundice.
Recognise
- Sensitised RhD-negative mother carrying an RhD-positive fetus
- Fetal/neonatal haemolysis: anaemia, hydrops fetalis, neonatal jaundice (early, <24h)
- Subsequent pregnancies more severely affected
Red flags
- Hydrops fetalis; severe fetal anaemia; rapidly rising neonatal bilirubin
Differentials & how to tell them apart
Investigations
Booking: blood group, rhesus status and antibody screen. Sensitised: monitor antibody titres + fetal middle cerebral artery Doppler (anaemia). Newborn: DAT (Coombs), bilirubin, FBC.
Management
Anti-D immunoglobulin prophylaxis (routine + after sensitising events)
- 1Routine antenatal anti-D prophylaxis for RhD-negative women: at 28 weeks (and historically 34 weeks).Gate: Give anti-D within 72 hours of any potentially sensitising event (bleeding, miscarriage/TOP, ECV, delivery of an RhD-positive baby, amniocentesis)
- 2Already sensitised (antibodies present): anti-D no longer helps — monitor with MCA Doppler ± intrauterine transfusion; treat the neonate (phototherapy/exchange).
Key points
Anti-D PREVENTS sensitisation but does NOT help once antibodies have formed. Kleihauer test quantifies fetomaternal haemorrhage to size the anti-D dose. Cord blood group/DAT at delivery.
Monitor & prognosis
Antibody titres, MCA Doppler; neonatal bilirubin/Hb.
Largely preventable with anti-D; treatable if it occurs.
Source: NICE; BCSH; RCOG