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POX Screening Decision Tool

Common Questions

New parents often have questions about screening tests done on their babies. Click below for answers to some of the most common questions about pulse oximetry screening for Critical Congenital Heart Disease. If you have questions that are not answered here, or if you would like more information about this screen, please ask your medical care provider or contact the Wisconsin SHINE Project.

Answers to Common Questions from Families

Question:Will pulse oximetry detect all forms of serious congenital heart disease?

No. Pulse oximetry is most useful in detecting heart defects with which a baby can look entirely well a day after birth and become very ill within the next few days. The heart defects that are most likely to cause serious congenital heart disease and are detectable by pulse oximetry are:

Heart Defects that are also likely to cause serious congenital heart disease in babies and are also detectable by pulse oximetry include:

Question:Does pulse oximetry replace other methods of detecting critical congenital heart defects?

No. Most babies with CCHD will be diagnosed by prenatal ultrasound or by physical exam after birth.   Pulse oximetry serves as one additional method of catching the 1 or 2% of babies with critical congenital heart disease that aren’t detected by prenatal ultrasound or newborn physical examination.

Question:How often will a child with a normal heart fail the screening process (false positive result)?
Screening after 24 hours of life and allowing a total of three chances to pass the screen will minimize the number of false positives in babies who have normal hearts. It is also important to remember that pulse oximetry screening may be abnormal in babies who have problems that are not related to the heart. Sometimes pulse oximetry screening will help identify babies that have problems with breathing or have infections. All babies who fail pulse oximetry screening should be examined by a health care provider to determine why the baby has low blood oxygen levels. The chance that a perfectly healthy baby will fail the pulse oximetry screening test is less than 1 in 1,000.
Question:If a child fails the screening, what is the chance that they have a potentially life threatening heart condition (positive predictive value)?
If done at least 24 hours after birth, the chance of a serious heart defect ranges from 21% to 26%.  Low oxygen saturation may also be due to other problems that might not yet have become apparent such as breathing problems, bacterial infection, or other disease.
Question:Why does it matter when the screening is done?
Oxygen saturations gradually increase in normal babies over the first several hours of life.  If pulse oximetry screening is done too early, some babies will fail the screening even if their hearts are normal.  However, by 24 hours, the vast majority of normal babies will have oxygen saturation greater than 95%. The average saturation for a 24-hour-old baby is 97%.
Question:What should be done if a baby fails the screening test?
The first step is to examine the baby closely for other medical problems that could result in low oxygen levels in the blood.  If these are identified, the baby should receive the appropriate care for their particular problem.  If there is no other cause for the low blood oxygen saturation, the baby should be evaluated for a critical congenital heart defect.  That evaluation will usually involve an ultrasound test of the heart called an echocardiogram.
Question:Are other tests helpful in excluding a critical congenital heart defect if a baby fails the screening and no other cause for the low oxygen saturation is identified?
Other cardiac testing may be useful in certain circumstances.  A chest x-ray may be helpful in looking for problems with the lungs.  An electrocardiogram may be helpful if a heart rhythm disorder is suspected.  Laboratory tests may help to determine the presence of infection or a metabolic disease.  As helpful as these tests may be, however, they probably aren’t adequate to exclude the possibility of a critical congenital heart defect.
Question:What if an echocardiogram can’t be performed where the baby is born?
If a baby fails the pulse oximetry screening process and no other explanation for the low oxygen saturation is identified, an echocardiogram may be needed.  In smaller communities and more rural hospitals, this may not be available.  In this situation, the health care staff caring for the baby will often discuss the situation with a neonatologist or a pediatric cardiologist.  The health care team caring for the baby may recommend that the baby go to another facility so that the echocardiogram can be performed.  Depending on the circumstances, additional testing or observing the baby a little longer in the local hospital may be appropriate.
Question:What if my baby is admitted to the Neonatal Intensive Care Unit (NICU)?
Babies admitted to the NICU should also be screened for critical congenital heart disease. Often, babies admitted to the NICU need extra oxygen. In this case, pulse oximetry screening will happen when your baby no longer needs extra oxygen. If your baby is going home from the NICU on extra oxygen, pulse oximetry will be done in the few days before you leave the NICU.
Question:Is Pulse Oximetry Required by Law?

Pulse oximetry screening for CCHD is required by law. In 2014 pulse oximetry screening for Critical Congenital Heart Disease (CCHD) was added to the Wisconsin Newborn Screening Program’s panel of conditions. This means that all babies are required to have pulse oximetry screening. Having your baby tested for this condition is important to the health of your baby. As a parent, you can refuse pulse oximetry screening if your religious beliefs and practices or personal convictions do not agree with this testing.