Objectives: Fetomaternal hemorrhage (FMH) refers to the passage of fetal blood into the maternal circulation before or during delivery. Besides the deleterious effects of anemia in the fetus, allo sensitization of the mother to red cell particularly Rh antigens may result in significant mortality/morbidity in the current fetus or in future gestations. HbF resist acid-elution to a greater extent than do normal cells and it can be detected by Kleihauer Betke method. The objective is to study the importance of Von Kleihauer Betke test and its application in identifying the red cells containing fetal hemoglobin (HbF) and to calculate its percentage of existence in mothers during labor, at Trichy SRM Medical College Hospital & Research Centre. Materials and Methods: To study the importance of Von Kleihauer Betke test and its application in assessing fetomaternal haemorrhage, intravenous blood samples were collected from all the mothers, who got admitted for labor at Trichy SRM Medical College Hospital & Research Centre during July 2017 – Sep 2017. Thin blood smears were prepared and stained by acid elusion method. The stained slides were examined for red cells containing HbF fewer than 100x oil immersion microscope by the investigators separately to reduce subjective variation. To calculate the number of red blood cells containing HbF in mother, Von Kleihauer Betke test formula has been used. Blood grouping test of the entire mother and their neonates also was done to identify the Rh typing. Von Kleihauer Betke test has been implicated to calculate the dosage of RhIG to be given in Rh negative mothers with Rh positive babies. Observation and result: Among 215 mothers involved in the study, HbF % range was observed to be within 0-2.0%. No significant percentage of fetomaternal haemorrhage exceeding 2% was observed in our study during the study period. Among the samples of 215 mothers studied, HbF range was lowest (0-0.5%) in 40% (n=88), mid-range (0.6-1.5%) in 42% (n=89) and higher range (1.6-2%) in 17% (n=38) only.