Significance of red-cell irregular antibodies in the obstetric patient.

Irregular antibodies were identified in 1.3% of obstetric patients who were delivered at the Royal women's Hospital, Melbourne. The most common antibodies found were anti-P1 and anti-Lewis, but, although these antibodies may cause difficulty in obtaining compatible blood if transfusion is required, they were not associated with haemolytic disease of the newborn. Immunization with other irregular antibodies, especially Rhesus subtype and Kell, may occur due to pregnancy alone or follow the combination of pregnancy and incompatible blood transfusion. Irrespective of the initial cause of immunization, these antibodies are often associated with haemolytic disease of the newborn which may be severe enough to result in perinatal death. As most irregular antibodies are found in patients with Rh-positive blood, the need for screening of all antenatal patients in each pregnancy must be recognized.