Thank you for all of your input. Our 1 hour rule is just something we've "always" done and predates me so I do not know the origin. The current package insert for the K-B stain states, "maternal blood sample should be collected in a syringe with a sterile needle or by evacuated technique, as soon after delivery as possible." The new maternity director at my hospital is questioning our policy for the 1 hr requirement, which is really the only reason I need to find some data or evidence for or against our policy. I'll keep digging but if anyone else finds out more info in the meantime. . .keep me posted. Thank you.