Victoria Police officers who pulled over a ute driving "erratically" in Melbourne's west have helped deliver a baby girl by the side of the road.

The father, Fernando Martinez, was speeding on Geelong Road just after midnight on Saturday when police pulled him over.

Bianca Martinez told the ABC that her husband got out of their ute, stuck his hands up in the air and said "my wife is having a baby".

A quick check of the front passenger seat revealed the man's wife was indeed in the late stages of labour, and officers helped deliver the baby girl just as paramedics arrived on the scene.