Revised guidelines advocate two doses of anti-D immunoglobulin for antenatal prophylaxis

EDITOR—In his editorial van Dijk advocates routine antenatal prophylaxis with anti-D immunoglobulin of all pregnant women who are RhD negative and refers to the consensus conference at the Royal College of Physicians in Edinburgh in April 1997.1 He states that two dose schedules were considered—two doses of 500 IU of anti-D immunoglobulin, one at 28 weeks' gestation and the other at 34 weeks, and one dose of 1000 IU given between 28 and 30 weeks—both options being equally effective. He implies that the second option reflects Bowman's practice in Canada.2 Bowman's programme in fact uses a dose of 1500 IU given at 28 weeks; maternal anti-D immunoglobulin concentrations are then monitored and additional anti-D immunoglobulin is given at around 36 weeks to those women in whom passive anti-D immunoglobulin is no longer detectable.

In my presentation to the conference the second option considered was a single dose of 1500 IU—not 1000 IU—of anti-D immunoglobulin at 30 weeks. In the final consensus statement the panel did not indicate a preference between these options and was satisfied that “both seem to work.” A dose of 1000 IU of anti-D immunoglobulin was never considered as the rate of its decay would mean that little or none would remain in a woman's circulation towards the end of pregnancy, when fetomaternal haemorrhage is known to occur more frequently.

Revised guidelines on the use of anti-D immunoglobulin from the British Blood Transfusion Society and the Royal College of Obstetricians and Gynaecologists agree that the preferred option is two doses of 500 IU of anti-D immunoglobulin.3 This option was chosen partly because it uses less anti-D immunoglobulin—a scarce resource—than a single dose of 1500 IU and partly because two doses of 500 IU given at 28 and 34 weeks achieve a higher circulating concentration of anti-D immunoglobulin as term approaches than does the single larger dose. The revised guidelines were also prompted by the absence of published data on the clinical outcome of giving a single dose of 1500 IU at 30 weeks.

Services should be centralised for pregnancies affected by RhD haemolytic disease

EDITOR—In their article on the underreporting of mortality from RhD haemolytic disease in Scotland, Whitfield et al highlight an important issue.1 We recently completed a study on the outcome of all pregnancies affected by RhD antibody in Northern Ireland from October 1994 to February 1997 (presented at the autumn 1997 meeting of the Irish Perinatal Society, Portiuncula Hospital, Country Galway, Republic of Ireland). Of the 124 pregnancies affected by RhD antibody, five were spontaneous abortions, one a stillbirth of unknown cause (no signs of hydrops), and two stillbirths after intrauterine blood transfusions—one at 25 weeks' gestation and the other at 27 weeks. Only one neonatal death (1.6 per 10 000 live births) was reported.

Mortality should not, however, be the only concern with RhD haemolytic disease. Of the 78 babies affected by RhD isoimmunisation in our study, five had minor developmental problems and two had major permanent neurodevelopmental problems at 2 years of age. Thirty two of the 124 babies were born in hospitals that could not offer paediatrician led neonatal care, and nine of these babies had to be transferred to another hospital for their care.

We support the introduction of routine antenatal prophylaxis with anti-D immunoglobulin as this has repeatedly been shown to reduce the rate of maternal alloimmunisation. Given the morbidity and mortality associated with RhD haemolytic disease, a reduction in the disease's incidence should lead to both short and long term health gains for vulnerable babies.

To accompany the introduction of an antenatal prophylaxis programme with anti-D immunoglobulin we advocate the centralisation of services for affected pregnancies; with fewer affected mothers and babies, the training and maintenance of skills for obstetricians and neonatologists can only be guaranteed in this way.