Improved protection at term with an alternative strategy of prophylactic
anti-D administration in pregnancy - a prospective interventional study
Abstract
Objective: To analyse the proportion of RhD negative women where routine
antenatal anti-D prophylaxis (RAADP) in gestational week (gw) 28 is not
detectable at delivery and to investigate if a strategy with RAADP
administered in gw 28 and 38 result in efficient protection at term,
postterm and postdelivery. Design: A retrospective database analysis and
a prospective interventional study. Setting: Antenatal centers in the
Stockholm region. Sample: RhD negative women carrying an RHD positive
fetus, 4280 cases evaluated retrospectively, 39 cases included
prospectively. Methods: In a retrospective analysis, RhD negative women
with a negative antibody screen at delivery was determined. In 39
pregnancies, quantification of anti-D was analysed before a second dose
anti-D was administered in gw 38, and then weekly up to 43 weeks post
gestation. Main outcome measures: The proportion of women with
non-detectable anti-D at term. The concentration of anti-D measured
weekly at term, postterm and postdelivery. Results: In 20,5% (856/4280,
retrospective analysis) and 44% (17/39, prospective study) RAADP in gw
28 was below screening detection level, 10 IU/L at term and in 18%
(7/39, prospective study) below 1 IU/L in the quantification assay.
Anti-D prophylaxis administered in gw 38 showed stable protective levels
of anti-D up to 30 days postdelivery, with concentration at delivery
60+34 IU/L (mean+SD). Conclusion: At least one third of the RhD negative
women have non-detectable levels of RAADP given at gw 28, at term and
postterm. A second dose of RAADP at gw 38 improves the protection.