Setting
To prevent RhD immunization induced by pregnancy, RhD-negative mothers carrying RhD-positive foetuses receive both antenatal (around 30 weeks gestation) and postnatal anti-D prophylaxis (RhIg) in the Netherlands.
All pregnant women are screened for the presence of allo-antibodies in the first trimester of pregnancy. Furthermore, RhD-negative and c-negative women are additionally screened in week 27. The coverage of this screening program is almost 100%.8 All maternal blood samples with a positive screening result, identified at routine screening or at any other moment in pregnancy, are sent to one of the two national referral laboratories (Sanquin Diagnostic services and Special Institute for Blood group Investigations (BIBO)). Here, the clinical relevance of the antibody is evaluated by, amongst others, assessing whether the foetus is antigen-positive, with serological typing of the father as the first step in most of the pregnancies in this study. If the foetus is RhD-positive, the risk on foetal haemolysis is assessed by serially determining the antibody titer and antibody-dependent cell-mediated cytotoxicity (ADCC, performed only at Sanquin Diagnostic Services), a monocyte based assessment of the destructive capacity of the antibodies.9, 10