Quantification of fetomaternal haemorrhage and its application in Anti-d dosing in rhesus negative mothers delivering at Moi Teaching and Referral Hospital Eldoret.

Abstract

Background: Fetomaternal hemorrhage (FMH) is the entry of fetal blood into the maternal circulation during pregnancy or delivery. If this occurs in a Rhesus negative woman carrying a Rhesus positive fetus, there is a risk of the mother being sensitized against the D antigen. The effect is seen in the subsequent Rhesus positive pregnancies resulting in hemolytic disease of the fetus and newborn (HDFN). To prevent this sensitization, anti-D immunoglobulin is usually given. The dose given varies depending on the amount of FMH and protocols adopted by different professional authorities. There is limited local data on the determination of size of FMH and its utility in the dosing of prophylactic anti-D. The protocol in use in MTRH which is based on studies done in the West, recommends a uniform dose of 300µg irrespective of size of FMH, with no recommendation on quantification. Several studies have shown that lesser doses of anti-D can safely be used with lower cost implications. Objectives: To determine the prevalence of Rhesus negativity, quantify the size of FMH and to determine the average calculated dose of anti-D immunoglobulin required for postpartum prophylaxis in Rhesus negative women delivering at MTRH. Methods: This was a cross-sectional study conducted between April and September 2017. It involved estimation of size of fetomaternal hemorrhage, using the Kleihauer Betke test, on a sample of venous blood collected from Rhesus negative postpartum women within 2-12 hours after delivery. Consecutive sampling was used. Structured questionnaires were administered to eligible participants. Data analysis was done using R version 3.3.3 (R Core Team, 2017). Results: Out of 4,552 deliveries over the study period of six months, 143 (3.1%) women were Rhesus negative. Of the 143 women, 99 met the eligibility criteria and were included in this study. The mean age was 26.4 years and mean gestational age at delivery was 39 weeks. Fetomaternal hemorrhage was detected in 35 (35.4 %) of the study participants, 24 (68.6%) of whom had FMH of less than 10ml. The size of FMH ranged from 2.5-20mls. The use of 100µg of anti-D immunoglobulin would have been sufficient for 89.9% (89/99) of the Rhesus negative mothers in whom quantification of FMH was done. Conclusion: The prevalence of Rhesus negativity among deliveries in MTRH was 3.1%. FMH of less than 10ml occurred in 89.9% of study participants thus indicating that majority of the cases of FMH could have been neutralized by 100µg of anti-D immunoglobulin. Recommendations: We recommend quantification of FMH in all unsensitized Rhesus negative women after delivery and accordingly adjusted dosing of anti-D immunoglobulin.