What is average heart beat of a fetus at birth?

I would expect the heart rate to be zero as a fetus would be non viable outside of the womb.

If you meant a child at the time of birth, that's different.

A typical newborn right at birth (and prior to it) will have a heart rate somewhere between 110-160 on average.

Once born, this typically slows a little bit but is still in a range of about 90-160.

The average heart rate continues to slow through childhood until it reaches an average of 60-100 (the adult range) by the teenage years.