An expectant mother has lost her unborn child after she was involved in a serious car crash south of Brisbane.

The woman, 30, was a passenger in a Nissan Maxima that was in a collision with a Holden Commodore at an intersection in Marsden about 7.45pm on Friday.

The woman was 38 weeks pregnant and was taken to the Royal Brisbane Hospital, an ambulance spokesman said.

Police have since revealed she lost her unborn baby as a result of the crash.

The driver of her car, a 39-year-old man, along with two children – a 10-year-old boy and 18-month-old girl – were taken to Logan Hospital with minor injuries.