A 1-day-old newborn has just expelled a thick, greenish-black stool. What should the nurse do next?

The appropriate action in this scenario is to document the stool in the infant's record. The thick, greenish-black stool observed in a 1-day-old newborn is referred to as meconium. Meconium is the first stool that a newborn passes and is composed of material ingested during the time in the womb, including amniotic fluid, bile, and cells.

Documenting the stool is crucial for ongoing patient assessment and helps establish a baseline for the infant's bowel movements. It provides important information regarding the normal progression of bowel movements, as the stool color and consistency can signal various stages of the infant’s transition from prenatal to postnatal life.

While notifying the pediatrician might be necessary for other concerning findings, in this case, passing meconium is a normal and expected occurrence. Administering a laxative is not appropriate, as it is unnecessary for a newborn who is simply passing meconium. Monitoring the infant’s temperature is also part of routine care, but it does not directly relate to the context of meconium passage in terms of immediate next steps. Thus, documenting the stool is the most relevant and appropriate course of action following this observation.