A 28-year-old woman and her 13-year-old nephew are in serious condition in hospital after a single vehicle car crash just outside of Sydney Thursday night.

Police said the car the woman was driving left Frenchvale Road and went over a 12-metre embankment and traveled 24 metres into the woods at about 7 p.m.

The 13- year-old was thrown from the vehicle and the woman was trapped inside.

The Cape Breton Regional Police are reminding people to wear seatbelts.