Unless you live in one of the very few states that requires parental consent, there is a good chance that no one will inform you about the newborn screenings unless your baby is within your sight at all times. You might not ever know when (or if) the screenings were done unless you are paying attention. Look for a bandage on your baby's heel; this is the surest sign that a PKU test has been done. And, of course, you can always ask.
If your baby has no bandage (check the heel for a red mark, which usually lasts awhile, just in case the bandage already fell off), it's possible that somebody forgot to do the screening. Don't see a mark or a bandage on the heel? Look for a bandage elsewhere (such as on the hand) in case a regular blood draw was used instead of a heel stick.
You usually won't hear anything about the results. In this case, no news is good news. However, since things sometimes fall through the cracks, it doesn't hurt to ask just to make sure all the results came back normal.
What If PKU Doesn't Run in My Family?
Just because nobody in your family has ever had PKU doesn't mean your child won't either. PKU is an autosomal recessive mutation. If you remember back to your high school or college science classes, you might recall that this means a baby has to get two "bad" copies (one from each parent) in order to develop the disease. If you only have one "bad" copy, you won't have the disease. So it's entirely possible for two non-PKU parents to have a baby with PKU.
PKU is a rare but devastating disease. Because there is a treatment (dietary restriction of phenylalanine) that clearly will help reduce the effects of the disease, and because testing is easy and inexpensive, it's generally recognized that universal newborn screening is worthwhile.
U.S. National Library of Medicine and National Institutes of Health. Phenylketonuria (June 17, 2011). MedlinePlus Web site. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/001166.htm. Accessed October 1, 2013.
Kock RK. Issues in newborn screening for phenylketonuria. Am Fam Physician 1999;60(5):1462-1466.
Hanley WB, Demshar H, Preston MA, et al. Newborn phenylketonuria (PKU) Guthrie (BIA) screening and early hospital discharge. Early Hum Dev 1997;47(1):87-96.
Doherty LB, Rohr FJ, Levy HL. Detection of phenylketonuria in the very early newborn blood specimen. Pediatrics 1991;87(2):240-4.
American Civil Liberties Union. Newborn DNA banking (n.d.). ACLU Web site. Available at: https://www.aclu.org/free-speech-technology-and-liberty-womens-rights/newborn-dna-banking. Accessed October 1, 2013.
Larsson BA, Tannfeldt G, Lagercrantz H, Olsson GL. Venipuncture is more effective and less painful than heel lancing for blood tests in neonates. Pediatrics 1998;101(5):882-6.
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