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