ATYPICAL ANTIBODY SCREEN
Before giving prophylactic RhoGAM to an Rh-negative woman, an indirect
Coombs test is performed at 28 weeks. This is obtained to ensure she has not
become isoimmunized since her previous negative AAT earlier in pregnancy.
Two-tenths of a percent of Rh-negative women will become isoimmunized
from spontaneous feto-maternal bleeding before 28 weeks.
If it is discovered that the patient already has anti-D antibodies, administration
of RhoGAM is futile.http://ebookobgyne.net