Postpartum anti‐D: can we safely reduce the dose?

Abstract

Objective: To assess the potential for dose‐reduction of prophylactic anti‐D postpartum. Design: Retrospective audit of fetomaternal haemorrhage (FMH) quantitation by flow cytometry. Participants and setting: 5148 consecutive Rhesus D‐negative women aged 15–45 years who had FMH estimation by flow cytometry at a central laboratory in Western Australia in the 65 months between 1 August 1999 and 31 January 2005. Main outcome measures: Quantitation of FMH volume for adequate prophylactic anti‐D administration in a timely fashion. Results: 90.4% (4651/5148) of the women had an FMH volume of 1.0 mL or less of Rh D‐positive red cells, and 98.5% (5072/5148) had a volume of less than 2.5 mL. Only 0.4% of cases had an FMH volume of 6.0 mL or greater (range, 6.0–92.4 mL). Conclusions: This large retrospective audit shows that a currently available dose of 250 IU (50 mg) of anti‐D would have been sufficient for 98.5% of the 5148 Rh D‐negative women. On the basis of this evidence, a reduction in the recommended routine postpartum dose of anti‐D from 625 IU to 250 IU when flow cytometric quantitation for FMH is available should be considered. Adopting such a strategy would ensure the ongoing provision of a valuable human blood product currently in limited supply.

Assessment of Fetomaternal Hemorrhage in Rhesus D-negative Postpartum Women by Kleihauer—Betke Test

“…Administration of 100 μg of RhD immunoglobulin that is equivalent to 5 mL of FMH would be sufficient for a large number of population. This result was consistent with the result revealed by Augustson et al, 17 in which they concluded that 90.4% (4651/5148) of the women had FMH volume of 1.0 mL or less of Rh D-positive red cells, and 98.5% (5,072/5,148) had a volume of less than 2.5 mL. Only 0.4% of the cases had an FMH volume of 6.0 mL or greater (6.0-92.4 mL).…”

Fetomaternal hemorrhage in normal vaginal delivery and in delivery by cesarean section

“…In approximately 1.5% of deliveries, FMH exceeding 5 mL of whole fetal blood occurs, in only 1% of deliveries the fetal blood volume entering maternal circulation exceeds 12.5 mL, and in only 0.5% of deliveries it exceeds 25 mL 13‐16 . However, in nearly 50% of all cases no risk factor is present 15‐17 …”

Fetomaternal hemorrhage in women undergoing elective cesarean section

“…Other investigations have previously demonstrated FMH > 15 ml fRBCs in 1–6% of all deliveries (7–10,12), but most of these investigations were performed using the Kleihauer–Betke method. A retrospective Australian audit of FMH assessed by flow cytometry indicated that 25 of 5,148 women (0.4%) had >3 ml fRBCs (3–46.2 ml) (17). No clinical data were reported and no subdivision of data showing the distribution of women having 3–15 ml and those having >15 ml fRBCs was reported.…”