Altered strategy of prophylactic anti‐D administration in pregnancy to cover term and post‐term – a pilot study. Issue 9 (27th March 2021) - Wikman, Agneta
Abstract : Background and objective: Routine antenatal anti‐D prophylaxis (RAADP) to RhD‐negative women is most often administered in gestational age (GA) 28–30 weeks with the next anti‐D dose administered postpartum. The aim of this study was to analyse the proportion of RhD‐negative women where RAADP is not detectable at term and in a pilot study to investigate whether RAADP administered in GA 28 and 38 results in detectable levels at term, post‐term and post‐delivery. Materials and methods: In a retrospective analysis, 4280 RhD‐negative women carrying an RHD positive fetus were included and the proportion with a negative antibody screen at delivery was determined. In the second part, 39 pregnancies were included prospectively, a second dose of RAADP was administered in GA 38 weeks, and anti‐D was quantified before the second dose and then weekly for 5 weeks. Results: In the retrospective analysis, 20·5% (856/4280) with RAADP administered in GA 28 were negative in routine antibody screening at delivery. In the small prospective study, 18% (7/39) had a negative antibody screen and 26% (10/39) had levels below 0·005 IU/ml, in the quantification assay, in GA 38. Anti‐D prophylaxis administered in GA 38 showed detectable levels of anti‐D up to 30 days post‐delivery, with concentration at delivery 0·060 ± 0·034 IU/ml (mean ± SD). Conclusion: Approximately 20% of the RhD‐negative women show non‐detectable levels of anti‐D at term. A second dose of RAADP at GA 38 results in stable concentrations of anti‐D at term, post‐term and post‐delivery, but with large interindividual variation.