Quantification of FMH is essential for determination of an accurate dose of anti-RhD Ig in antepartum and postpartum immunoprophylaxis of HDFN. Doses of anti-RhD are established with reference to the volume of RhD positive foetal red blood cells in the circulation of RhD negative voluntaries. Results obtained from flow cytometry, microscopic Kleihauer-Betke test or serological test indicate percentage of these cells.
The aim of the study: To compare results of FMH volume calculation using various formulas.
Material and methods: EDTA blood samples from 51 mothers and 51 cord blood samples from their newborns were analyzed. Five formulas were based on following parameters: percentage of foetal red blood cells in the blood sample from mother, mother's body weight and Hct, maternal and foetal MCV.
Results: The range of maternal Hct was 25.7-46.2% (mean 34.3%), ratio of foetal MCV to maternal MCV was 1.09-1.41 (mean 1.19), body weight of mothers 56-99 kg (mean 73.5 kg) and calculated volume of their blood 3600-7425 mi (mean 5100 ml). For 0.4% FMH we predicted 2, 3 or 4 doses of anti-RhD Ig 500 IU (100 microg) and 1, 2 or 3 doses of anti-RhD Ig 750 IU (150 microg) depending on the woman.
Conclusions: The formula with individual maternal and foetal morphological parameters is much more accurate for calculation of the volume of FMH and doses of anti-RhD Ig than often used formula with average values of the parameters.