Are you saying you do not do the K-B if the FMH screen is negative? According to the screen package insert it says that with a weak D infant the screen may not be positive even with a greater that 30ml. bleed. We are currently not following a negative screen with a K-B, although I am not sure how many if any infants we have had in these cases that are weak D since we report these babies out as RhD positive.