This is the heart-stopping moment a pregnant motorcycle passenger with quick reflexes dodged a loose wheel that came hurtling towards her head.

The girl was riding pillion with her boyfriend and pulling out into the road when they noticed the hazard approaching in Prachuap Khiri Khan, southern Thailand.

Dashcam footage from a parked car shows how the astonishing scene unfold on December 3.

The young man riding the bike was startled and stopped, before frantically trying to push the vehicle backwards.

However, his young partner - who was in the direct back of the deadly projectile and six-months pregnant - had to clamber off the bike and duck to avoid being hit.

Miraculously, they both escaped unharmed and reported the incident to the police, who tracked down the owner of the wheel.

The driver, Khun Nonee, was summoned for questioning and settled the issue privately with the couple.

She said: ''The people on the motorcycle weren't hurt. The girl was pregnant but she's OK. It was my wheel from my truck carrying pineapples, but it was an accident. it just came away without me realising. I don't know why.''