ANTI-D ADMINISTRATION IN EARLY-PREGNANCY - TIME FOR A NEW PROTOCOL

The use of anti-D immunoglobulin has dramatically reduced the incidenc e of rhesus isoimmunization arising from pregnancy. A critical shortag e of anti-D has developed and consumption must be reduced, preferably without increasing the risk of isoimmunization. The standard dosage of anti-D currently given at all gestational ages is 1 ampoule containin g 125 ug of anti-D. Of the anti-D administered half is during the firs t trimester when a much lower dose could be used; 30 ug would remove f rom the maternal circulation the entire fetoplacental blood volume (3 ml) of a 12 week's pregnancy. A dose of 30 ug would also be adequate f or most fetomaternal transfusions after 12 weeks but prior to the thir d trimester. A larger dose could be administered if maternal Kleihauer resting suggests the need for a supplementary dose. In the third trim ester, the current regimen is appropriate - a dose of 125 ug of anti-D supplemented when needed on the basis of maternal Kleihauer testing. A lower dose ampoule of anti-D should be available. In addition, exist ing protocols for anti-D administration should be modified so that sma ller more appropriate doses are given, better utilizing the limited su pply of anti-D.