The critical antibody titre above which the fetus is at significant risk of severe haemolytic disease of the fetus/newborn (HDFN) requiring invasive surveillance (MCA Doppler/amniocentesis) is:
- A Anti-D titre ≥1:4
- B Anti-D titre ≥1:8
- C Anti-D titre ≥1:16 ✓
- D Anti-D titre ≥1:64
Explanation
A maternal anti-D titre of 1:16 (or 16 IU/mL in some centres; 1:8 to 1:16 is the 'critical titre' threshold) is the widely accepted level above which the fetus is at significant risk of severe HDFN (hydrops fetalis, intrauterine death). At or above this titre, management escalates to middle cerebral artery (MCA) peak systolic velocity (PSV) Doppler surveillance every 1–2 weeks (MCA PSV >1.5 MoM indicates moderate-severe fetal anaemia, prompting cordocentesis or intrauterine transfusion). Below the critical titre, non-invasive monitoring with serial titres suffices. The threshold may be lower (1:8) in centres with prior sensitised pregnancies.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.