[Foetal Rhesus-D typing added to antenatal screening for infectious diseases and erythrocyte immunisation]

Investigation of the accuracy and national implementation of foetal Rhesus-D typing (fRhD), introduced in 2011 for RhD-negative pregnant women.

Descriptive, national study.

Results of fRhD in pregnant women in the first year after implementation were compared to results from cord blood RhD typing of the child.

0.05% of the fRhD results was false negative (9/18.383; 95% CI: 0.02-0.09), and 0.85% was false positive (157/18.383; 95% CI: 0.73-1.00). fRhD was incorrectly omitted in fewer than 1% of pregnant women. In 96.1% of the pregnant women, antenatal administration of anti-D prophylaxis was recorded. Recording of postnatal anti-D administration turned out to be lower (92%), but locally recorded data showed that postnatal anti-D was omitted in fewer than 2% of cases.

The percentage of false negative fRhD was statistically significantly lower (p < 0.05) than the critical limit of 0.25% determined beforehand by the Programme Committee of the Dutch Antenatal Screening Programme for Infectious Diseases and Erythrocyte Immunisation. The percentage of false positive fRhD was considered acceptable, and implementation of fRhD was more or less complete. Routine RhD-typing on cord blood was therefore omitted from January 2013. Antenatal and postnatal anti-D administration is now specifically indicated for RhD-negative pregnant women when fRhD is positive, thus saving about 10,000 unnecessary antenatal anti-D administrations per year. RhD-typing on cord blood is now performed only if the RhD blood type of the child of a RhD-negative mother is unknown at delivery, if a positive fRhD was found for multiple births, and in exceptional situations, e.g. if fRhD typing is not possible due to a rare genetic variation.