Bombay phenotype (O_h ) and high-titer anti-H in pregnancy: two case reports and a review of the literature

Background: Antenatal cases of Bombay-phenotype (O_h ) individuals and hemolytic disease of the fetus and newborn (HDFN) are not well described in the literature. We present two case reports of high-titer anti-H in pregnant O_h individuals and their serologic investigation, clinical management, and subsequent outcomes. We describe current published cases detailing pregnancy in O_h individuals, to add to the evidence base for clinical decision making and management of pregnancy.

Study design and methods: We describe two case reports of high-titer anti-H in pregnancy in O_h individuals. We summarize published cases to date, to inform clinical decision making and antenatal management in individuals with the Bombay phenotype.

Results: Of the case reports described, neither were affected by HDFN due to anti-H. Antibody titers were high in both cases (immunoglobulin G titer scores, 512 and 4000, respectively) and would be expected to cause some degree of HDFN, a surprising finding. Regular mean cerebral artery Doppler ultrasound was normal. Patient blood management (PBM) techniques ensured that the patient's hemoglobin (Hb) levels were monitored and maintained. Transfusion intervention was not required, with minimal blood loss recorded at birth in both cases.

Conclusion: High-titer anti-H in O_h pregnancies may, in rare cases, cause HDFN, but evidence suggests that this may not be the case in all pregnancies. We recommend a multidisciplinary approach, with prompt referral to a fetomaternal medicine unit, combined with PBM strategies, and a planned delivery with the provision of rare-phenotype units (if available and if indicated) on standby.