Is it dangerous to have a low heart rate for a term fetus in labor?

Depends. The fetal heart rate is expected to vary before and during labor. When contractions are strong, the stress on baby can alter the rate. A transient slowing during contractions with recovery between is expected. If it goes down low & altering mom's position some doesn't help it return, it can be a sign of fetal distress & lead to an urgent C-section.
It can be. Depends on how low & for how long & whether the heart rate dip is repetitive. Normal fetal heart rate at term in labor is about 110-160 bpm. An obstetrician will act accordingly depending on the above criteria.