This will be a prospective clinical study conducted with the approval of the Clinical Research Ethics Committee.

The influence of phototherapy lights on the accuracy of pulse oximetry will be investigated.

Each patient's oxygen saturation will be measured non-invasively via a nondisposable polyethylene neonatal probe taped to the infant's palm, toe, or dorsum of the foot. The probe will be connected to an Massimo Rad97 pulse oximeter that is standardized at the factory. It runs through an automatic systems check when turned on and needs no further calibration before being used. The oxygen saturation measurements will be considered valid when there will be a normal plethysmographic waveform, a fullscale signal strength bar, and a stable heart rate closely approximating an independent electrocardiographic (ECG) pulse rate. The pulse oximeter works by using the technology of plethsmography which allows the detection of an arterial pulse) with oximetry (which measures oxygen saturation at specific wavelengths). The pulse oximeter will be placed on each infant as already described. After a stable pulse oximeter reading was obtained, the value will be recorded ("before") and then the probe will be covered with a standard disposable diaper, shiny side up. When the reading stabilized, the value will be recorded ("during") and then the diaper will be removed.

Inclusion Criteria:

• newborn babies (0-28 days)
• to be treated in the Hacettepe University Children's Hospital Neonatal Intensive Care Unit
• receiving phototherapy treatment

Exclusion Criteria:

• Newborn babies with any diseases that affect oxygen saturation including congenital heart disease, chromosomal disease, inborn error of metabolism, anemia, circulatory disorder, hypovolemia or hydrops fetalis

All newborn babies who are receiving phototherapy for indirect hyperbilirubinemia in the NICU of the Hacettepe University will be included in the study following the obtaining of informed consent by their parents/guardian.

The oxygen saturation of all babies receiving inpatient treatment in the NICU is routinely monitored with a pulse oximeter. In this study, the oxygen saturation of the newborns receiving phototherapy will be recorded.