Occasionally a woman may decline to accept an injection of anti-D. It may be that she has religious or personal beliefs about accepting blood products, or that she believes she may not have any more children (although it is not a good time to make definite decisions about further children in the emotional time of pregnancy and early parenting).
If the woman is advised to have anti-D Immunoglobulin and she declines to accept it, it is advisable that she has a blood test 6 to 12 months after the birth to see if she has formed any antibodies, or prior to conceiving another child.
Information sources
Crowther C, Middleton P. Anti-D administration after childbirth for preventing Rhesus alloimmunisation (Cochrane Review). In: The Cochrane Library, Issue 2, 2002. Oxford: Update Software.
Gabbe S, Niebyl J R, Simpson J L, Pocket Companion to Obstetrics, Normal and Problem Pregnancies, 3rd Edition, 1999, Churchill Livingstone, New York