A three-year assessment of an action line method of timing intervention in rhesus isoimmunization

Abstract

The results achieved in 768 pregnancies with rhesus isoimmunization are described. An action line method, based on extrapolating the trend between separate measurements of the liquor bilirubin (by Liley's method), was used to determine the time for delivery or for intrauterine fetal blood transfusion in 510 pregnancies. A further 147 cases, in which the action line was not applicable, were managed correctly by alternative criteria. Correct management along these lines reduced the total rhesus mortality rate (including abortions) to 11.4 per cent and to 8.9 per cent if high-risk patients transferred from other rhesus centers are excluded. Reduction in mortality rate was particularly striking in first affected pregnancies (rhesus deaths in 3.6 per cent) and when previous babies had required exchange transfusion but had survived (rhesus deaths in 9.5 per cent). Unnecessary prematurity was almost eliminated in mildly affected and unaffected babies.