Use of cffDNA to avoid administration of anti-D to pregnant women when the fetus is RhD-negative: implementation in the NHS.

OBJECTIVE: To determine whether a policy of offering cffDNA testing to all RhD-negative women at about 16 weeks' gestation to avoid anti-D administration when the fetus is RhD-negative could be implemented successfully in the NHS without additional funding.

DESIGN: Prospectively planned observational service implementation pilot and notes audit.

SETTING: Three maternity services in the South West of England.

POPULATION: All RhD-negative women in a 6-month period.

METHODS: Prospective, intervention, cross-sectional observational study, using pre-intervention data as controls.

MAIN OUTCOME MEASURES: Proportion of suitable women who offered and accepted the test. Accuracy of the cffDNA result as assessed by cord blood group result. Fall in anti-D doses administered.

RESULTS: 529 samples were received; three were unsuitable. The results were reported as RhD-positive (n = 278), RhD-negative (n = 185) or inconclusive, treat as positive (n = 63). Cord blood results were available in 502 (95%) and the only incorrect result was one case of a false positive (cffDNA reported as positive, cord blood negative - and so given anti-D unnecessarily). The notes audit showed that women who declined this service were correctly managed and that anti-D was not given when the fetus was predicted to be RhD-negative. The total use of anti-D doses fell by about 29% which equated to about 35% of RhD-negative women not receiving anti-D in their pregnancy unnecessarily.

CONCLUSIONS: We recommend this service is extended to all UK NHS services.