A heavily pregnant Auckland woman has had a run in with a new Woolworths anti-theft trolley

Their wheels can lock electronically when passing over a boundary, or by remote control.

She says the trolley seized up for no apparent reason as she was leaving the Papakura store - smacking into her belly.

She says a store worker told her she was walking too fast.

Woolworths says it's an isolated incident and it's investigating with the supplier.