Newborn has a tiny vascular birthmark on lower midline back like a port wine stain and a tiny dimple in gluteal crease. is this likely tethered cord?

Sacral dimple: usually only a problem if the you can't see the bottom of the sacral dimple and usually if there is a problem it will also often leak cerebral fluid. as for the vascular birthmark, unless it is symptomatic I wouldn't worry about it. they usually regress by age 4

Tethered cord: Not likely. Do not stress. There are often birthmarks, patches of hair, and dimples at the base of the spine without tethered cord. Frequently, there are small variations of spine development that are not symptomatic and do not cause problems later in life. When the baby is older, an MRI of the lumbar spine can determine if there is an underlying abnormality.

Unlikely: a shallow sacral dimple is so common it is regarded as normal. If associated with a subcutaneous lipoma sometimes with hemangioma, or a deep dimple with a potential sinus tract, a tethered cord may be excluded in the neonatal period with ultrasound.