Positive red cell antibody screen (red cell alloimmunisation) in a pregnant woman

• State on the prescription: gestational age, RhD group, anti-D immunoglobulin injection (date, dose), previous transfusions.

Immunohaematology tests (if the laboratory has not already done them)

• Antibody identification
• Titration of the identified antibody
• Quantification of the antibody (anti-D, anti-c, anti-E, anti-Kell…)if neededAntibodies that can cause major fetomaternal incompatibility (anti-D, anti-c, anti-E, anti-Kell, etc.): quantification by antibody level, not combinable with titration under the fee schedule ^[2]; for anti-D, the SFTS recommends quantification techniques beyond standard titration ^[3].
• RH-Kell phenotype of the partner (antigen targeted by the antibody: c, E, Kell…)if neededRisk antibody other than anti-D: fetomaternal incompatibility is excluded only if the partner does not carry the antigen; if he carries it in the heterozygous state, doubt persists ^[4]. As long as the partner's phenotype or the fetal genotype is not informative, the pregnancy is monitored as incompatible ^[4].
• Fetal RhD genotyping on maternal blood (RhD-negative woman, from 11 weeks of gestation)if neededRhD-negative woman whose partner is RhD positive or of unknown group; a negative or indeterminate result is checked on a second sample, at least 15 days later and after 15 weeks ^[2,5].
• Fetal C, c, E or Kell genotyping on maternal blood (if anti-c, anti-E or anti-Kell with a heterozygous partner or one of unknown phenotype)if needednon-French guidelineRisk antibody other than anti-D, with a heterozygous partner or one of unknown phenotype: as long as this result is missing, the pregnancy is monitored as incompatible; the technique is available in France for C, c, E and Kell ^[4]. The Netherlands (2025) prefers it to the father's phenotype for anti-c and anti-Kell, and the UK (2025) proposes it ^[6,7]. In France, it has no fee-schedule code apart from RhD ^[2], and the expert centre following the pregnancy can arrange it.
• Partner's RhD blood group (if he has no blood group card)if neededRhD-negative woman: the partner's RhD group is to be documented; if he has no blood group card, prescribe it ^[5].