Final answer:
Nevus simplex and Mongolian spots may indicate an underlying problem that requires notification of the physician.
Step-by-step explanation:
The marks on a baby's skin that may indicate an underlying problem requiring notification of a physician are Nevus simplex and Mongolian spots.
Nevus simplex is a small lesion with an irregular border and parts that appear red, white, blue, or blue-black. It can be found on the skin.
Mongolian spots are large brown spots on the skin sprinkled with darker specks. They are commonly found on the lower back and buttocks of newborns with darker skin tones.