Synopsis
Interpret maternal red-cell antibodies, prevent avoidable sensitisation and organise antibody-specific fetal surveillance, transfusion planning and neonatal follow-up.
- Check ABO, D group and antibody screen at booking and 28 weeks, taking the latter sample before routine anti-D prophylaxis.
- Anti-D, anti-c and anti-K are major causes of severe fetal and neonatal disease; other antibodies can also matter.
- Anti-D prophylaxis prevents immune anti-D formation in eligible D-negative patients but does not treat established immune anti-D.
- Refer anti-D at 4 IU/mL or above, anti-c at 7.5 IU/mL or above, significant rises or an affected obstetric history for fetal medicine assessment.
- Use antigen status and antibody specificity to decide whether the fetus is at risk, then monitor with specialist MCA Doppler when indicated.
- Routine antenatal, sensitising-event and postnatal prophylaxis are separate decisions; a routine injection does not automatically cover another event.
Key red flags
Hydrops or persistently elevated MCA peak systolic velocity above 1.5 multiples of the median in an at-risk fetus requires urgent fetal medicine assessment.
A previous pregnancy requiring intrauterine transfusion or affected by severe haemolytic disease needs early specialist referral regardless of the current antibody level.
Anti-K detected for the first time needs fetal medicine referral because low titre does not safely exclude clinically important fetal disease.