Incidence of maternal sensitisation to Rh(D) in Christchurch, New Zealand and reasons for prophylaxis failures

Abstract

Aim: To estimate the current incidence of maternal sensitisation to Rh(D) and examine reasons for prophylaxis failures.

Method: Retrospective chart review of new sensitisations to Rh(D) detected in antenatal records, between 2005 and 2012 in Christchurch, New Zealand and systematic examination of circumstances likely to have caused prophylaxis failures.

Results: Fifty-four new sensitisations in an at-risk population of about 4624 in 8 years means an incidence of roughly 1.1%. In 86.6% of 45 sensitisations where information was available, there was a recognised sensitising event including previous deliveries while in 13.3% there were none. Of those with recognised sensitising events, 46.1% had anti-D prophylaxis per local guidelines, in 12.8%, prophylaxis was given though it did not conform, entirely, to guideline. No prophylaxis at all was given to 41% despite a sensitising event being recognised.

Conclusion: The incidence of maternal sensitisation to Rh(D) in Christchurch, New Zealand, is as expected given our prophylaxis regimen. Half the sensitisations were associated with complete or partial failure to follow local guidelines. Better adherence to this may reduce incidence of sensitisation. It is also thrice as high as might be expected with a routine antenatal anti-D prophylaxis (RAADP) program. An economic analysis of RAADP in New Zealand will be useful.