Hyperbilirubinemia and clinically significant jaundice represent two separate diagnosis. This is an important distinction.
Curious as to what you mean by "done improperly"? Are you referring to holding the baby above the level of the placenta? The idea of the baby transfusing the placenta is a myth. It's essentially impossible for this to happen due to the physiological processes in the cord after the birth. The muscular outer layer of the umbilical arteries spasm after the birth due to being outside of the warm womb. This shuts off blood flow in the umbilical arteries, thereby preventing backflow.
You might be interested to know that the WHO's definition of "early clamping" is somewhat different from the definition of "early clamping" used here in the US. In fact, the WHO advocates waiting at least 30 seconds to cut the cord. Studies here:
http://apps.who.int/rhl/pregnancy_childbirth/childbirth/3rd_stage/cd004074_abalose_com/en/index.html
http://apps.who.int/rhl/pregnancy_childbirth/childbirth/3rd_stage/jccom/en/index.html
http://apps.who.int/rhl/pregnancy_childbirth/childbirth/3rd_stage/jcguide/en/index.html
http://apps.who.int/rhl/pregnancy_childbirth/childbirth/3rd_stage/cd003248/en/index.html
Also of reference would be the editorial and study in the February edition of the Green Journal. If you have access to this edition, the page numbers are p. 203-204 for the editorial and p. 205-211 for the study. Interesting quote: "Delayed clamping of the umbilical cord has been known for decades to confer benefit to term infants by increasing their hemoglobin mass and iron endowment with no apparent adverse effects, except a modest increase in hyperbilirubinemia."
ETA: That would be the February 2011 edition, sorry. And by the "Green Journal" I mean "Obstetrics and Gynecology", the official journal of ACOG. If anyone would like a copy of the articles in question, feel free to PM me.