Pregnant women with red cell antibodies, who are assessed as being at high risk of requiring a blood transfusion, should have a cross-match sample taken at least every week.

Current BCSH guidelines require a sample no more than 72 hours old for providing compatible blood in
pregnancy,but do allow a deviation to the 3-day rule for individual cases such as high-risk women with placenta praevia without red cell antibodies where weekly samples can be taken, as long as a risk assessment is made and recorded in each individual case

In high-risk women with red cell antibodies where a sample every 72 hours is not feasible, a sample should be taken once a week and if transfusion is required a new sample should be taken immediately, to exclude new antibody development. However, in the event of life threatening haemorrhage, urgent transfusion should not be delayed and close liaison with the hospital transfusion laboratory is vital.