This is because phototherapy can cause dehydration and increase insensible water loss, so covering the genitalia can prevent excessive fluid loss and maintain thermoregulation.

Some possible explanations for the other choices are:

• Choice A is wrong because monitoring skin temperature every hour is not enough to prevent hyperthermia or hypothermia during phototherapy. The skin temperature should be monitored continuously or at least every 15 minutes.

• Choice C is wrong because repositioning newborn every 4 hours is not frequent enough to prevent pressure ulcers, skin breakdown, or eye damage from the light source. The newborn should be repositioned at least every 2 hours.

• Choice D is wrong because encouraging parent-infant interaction as tolerated is not a specific intervention for phototherapy.

While parent-infant interaction is important for bonding and development, it should not interfere with the effectiveness of phototherapy. The newborn should be exposed to the light as much as possible, except for feeding and diaper changes.

Normal ranges for serum bilirubin levels vary depending on the age, gestational age, and risk factors of the newborn. Generally, the levels should be below 5 mg/dL for term infants and below 7 mg/dL for preterm infants by the fifth day of life.