ANTENATAL PROPHYLAXIS OF RH ISOIMMUNIZATION - 28-WEEKS-GESTATION SERVICE PROGRAM

  • 1 January 1978
    • journal article
    • research article
    • Vol. 118  (6) , 627-630
Abstract
Two (0.18%) of 1086 Rh-negative primigravidas or multigravidas, who were given a single injection of Rh immune globulin (300 .mu.g) at 28 wk gestation and subsequently were delivered of Rh-positive babies, had demonstrable Rh isoimmunization at the time of that injection. The patients must be considered logistic failures of antenatal prophylaxis. The remaining 1084 (who were treated again after delivery) had no evidence of Rh isoimmunization at delivery and none of the 512 screened at 6 mo. after delivery appeared to be immunized. If the 28th wk injection was not protective, 14 of the 1084 would probably have been demonstrably Rh isoimmunized, and evidence of Rh isoimmunization would probably have persisted in 6 of the 512 observed 6 mo. after delivery. Six of 719 Rh-negative multigravidas who had not received Rh immune globulin after previous pregnancies or were treated only after delivery, showed evidence of Rh isoimmunization despite a single injection of Rh immune globulin at 28 wk in a subsequent pregnancy. In 3 of the 6 the cause was most likely sensibilization due to previous exposure to Rh-positive blood or an untreated Rh-positive pregnancy. In 3 of the remaining 716 (0.42%) there may have been true failure of antenatal Rh prophylaxis administered at the 28th wk. One would have expected this figure to be 12 of 716 if antenatal Rh prophylaxis at 28 wk gestation were totally unsuccessful. A single i.m. injection of Rh immune globulin, 300 .mu.g, is 88% effective in preventing Rh isoimmunization during pregnancy in Rh-negative primigravidas and in multigravidas treated antenatally in all previous pregnancies. The immune globulin is 75% effective in preventing Rh isoimmunization in Rh-negative multigravidas untreated during previous pregnancies. The majority of failures are due to Rh isoimmunization during pregnancy prior to antenatal prophylaxis at 28 wk.

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