The Management of Women with Red Cell Antibodies during Pregnancy

This guideline covers management once maternal red cell alloantibodies have already been detected — i.e. surveillance and treatment of the alloimmunised pregnancy. For prevention of RhD sensitisation (routine and event-driven anti-D immunoglobulin), see gtg-22.

Antibody Identification and Quantification

• Any clinically significant red cell antibody detected at booking or the routine 28-week screen should trigger identification and quantification, and referral for specialist input.
• Anti-D and anti-c are quantified in IU/mL (not titred). Anti-K and other antibodies (e.g. anti-E, anti-Fya) are generally reported as a titre rather than quantified, because Kell antibodies suppress fetal erythropoiesis directly and titre correlates poorly with disease severity.
• Anti-K: refer to a fetal medicine specialist on first detection, regardless of titre or history, because of the risk of severe fetal anaemia independent of antibody level.
• Other non-D, non-c, non-K antibodies: referral is prompted by a titre of 32 or above, or by a history of a previously affected pregnancy (prior HDFN or intrauterine transfusion), particularly if the titre is rising.

Antibody Surveillance Schedule

• Anti-D/anti-c levels are conventionally banded: <4 IU/mL — HDFN unlikely; 4–15 IU/mL — moderate risk (unlikely to be severe but needs monitoring); >15 IU/mL — significant risk of severe HDFN/hydrops.
• Repeat antibody quantification approximately every 4 weeks up to 28 weeks' gestation, then increase to fortnightly from 28 weeks to delivery.
• Once a level/titre crosses the referral threshold (or in a woman with a prior affected pregnancy), routine serology surveillance is superseded by fetal surveillance with serial Doppler.

Doppler Surveillance for Fetal Anaemia

• Middle cerebral artery peak systolic velocity (MCA-PSV) is the non-invasive surveillance tool of choice for fetal anaemia in alloimmunised pregnancies, replacing serial amniocentesis for bilirubin (ΔOD450).
• Serial MCA-PSV scanning is performed from around 18–20 weeks (or once antibody levels cross the referral threshold) at intervals of roughly 1–2 weekly, by an operator experienced in the technique, up to about 35–36 weeks (beyond which sensitivity falls).
• A rising MCA-PSV trend, or a value ≥1.5 multiples of the median (MoM) for gestation, indicates a high probability of moderate-to-severe fetal anaemia and should prompt referral to a fetal medicine centre for confirmatory assessment and consideration of intervention.

Intrauterine Transfusion (IUT)

• Fetal anaemia suspected on MCA-PSV is confirmed by fetal blood sampling (cordocentesis), with IUT performed in the same procedure if anaemia is confirmed.
• IUT is indicated for confirmed significant fetal anaemia, particularly with an MCA-PSV persistently ≥1.5 MoM, rising titres/levels in a woman with a previously severely affected pregnancy, or evidence of hydrops.
• IUT is best performed in a specialist fetal medicine centre with access to compatible, irradiated, CMV-negative, freshly cross-matched red cells.
• Serial transfusions are typically required every 2–4 weeks until delivery; MCA-PSV becomes less reliable for predicting anaemia after a fetus has already received a transfusion.

Delivery and Postnatal Management

• Timing of delivery is individualised, balancing the risks of prematurity against ongoing alloimmune disease; many uncomplicated, well-surveilled cases proceed towards term, while a history of IUT or hydrops favours earlier, planned delivery in a unit with neonatal support.
• Cord blood should be sent at delivery for direct antiglobulin test (DAT/Coombs), full blood count, and bilirubin; the neonate needs monitoring for hyperbilirubinaemia and may require phototherapy, exchange transfusion, or "top-up" transfusions for late anaemia.

High-Yield Exam Points

• Anti-K disease does not correlate with titre — refer to fetal medicine on first detection regardless of level.
• Anti-D/anti-c are quantified in IU/mL; other antibodies are titred, with a titre ≥32 (or prior affected pregnancy) prompting referral.
• MCA-PSV, not amniocentesis/ΔOD450, is the modern non-invasive surveillance method for fetal anaemia.
• MCA-PSV ≥1.5 MoM = high probability of fetal anaemia → confirm with fetal blood sampling ± IUT.
• MCA-PSV loses predictive accuracy after a fetus has already had an IUT.
• This guideline is prevention-independent — anti-D prophylaxis to prevent sensitisation is a separate topic (gtg-22).

Source: RCOG Green-top Guideline No. 65 (Archived — content below remains clinically relevant unless a successor is found) (First published May 2014 (first edition). RCOG has since archived this guideline; the British Society for Haematology's "Guideline for the investigation and management of red cell antibodies in pregnancy" (2016, updated 2025) is the current successor and covers the same scope.)

Read the original on rcog.org.uk

Clinically reviewed by NHS obstetricians and gynaecologists · Source last updated First published May 2014 (first edition). RCOG has since archived this guideline; the British Society for Haematology's "Guideline for the investigation and management of red cell antibodies in pregnancy" (2016, updated 2025) is the current successor and covers the same scope.

MRCOG AI is an independent educational tool. It is not affiliated with, endorsed by, or connected to the Royal College of Obstetricians and Gynaecologists (RCOG).