[1] However, publications have shown that in comparison with flow cytometry methods, the KB Test overestimates FMH due to false positive results when F-cells are present in the maternal blood sample.

For determination of the intracellular distribution of Hemoglobin F, the semi-quantitative method of Shepard, Weatherall, and Conley' may be employed.

Normal values for Hemoglobin F cells in adults as published originally by Kleihauer were below 0.01%; in full-term newborns they are above 90%.

To determine if a positive test for FMH indicates the likely cause of fetal death, the percent of total fetal blood volume lost should be calculated, making appropriate adjustments based on the following known relationships: These constraints can then be applied to yield the formula where An estimate of the required number of Rho(D) immune globulin vials may assume the following equations:[6] Combining those two equations results in:[6] This is approximately equal to: Practically, if the number to the right of the decimal point is ≥5, it is rounded up to add one vial.

with a stillbirth, though in many cases, given other information, such as known hereditary complications of pregnancy, extremely high positive correlation coefficients

However, if the mother and fetus are ABO incompatible, it is more crucial to quickly perform the KB stain following a stillbirth, as the fetal red blood cells will be eliminated from the maternal bloodstream quickly, causing the KB stain to underestimate the degree of FMH, if any.

Delivery does result in higher frequency of detection of micro-hemorrhages but this should not confound interpretation of FMH as a possible cause of stillbirth.

However, if Caesarean section is to be used, failure to draw the sample prior to that will result in a 2% false positive rate.

[citation needed] Finally, anything which causes persistence of fetal hemoglobin in maternal blood cells will make interpretation much trickier.

An article published in 2004 concluded that a Kleihauer-Betke (KB) test is necessary in all cases of maternal trauma, as clinical evaluation is not sensitive enough for determination of risk of pre-term labour.

It accurately predicts the risk of preterm labor after maternal trauma whereas the article concluded that clinical assessment does not.

With a negative KB test, posttrauma electronic fetal monitoring duration may be limited safely.

With a positive KB test, the significant risk of pre-term labour mandates detailed monitoring.