The star was on her way to pick up her daughter Lexi at school in West London when her car collided with a truck.
A bystander came to Holden's rescue by taking her to a nearby hospital for a check-up.
A spokesperson for the actress insists both Holden and her unborn baby are fine, but the star dropped out of a performance of Shrek The Musical to recover.
The rep adds, ""The lorry's (truck) fine, Amanda's car isn't. Amanda is so grateful to her good Samaritan.""
The 40 year old announced she's expecting a girl last month (Aug11), after previously miscarrying a boy earlier this year (11).