THE trial of a mum who was driving when her 4WD crashed near Bororen resulting in the death of her nine year-year-old son has been delayed because she is pregnant.

Mother of six Olivia Meagan Cullinane, 39, is pregnant with her seventh child, the District Court in Gladstone was told.

Cullinane, from Nambour, is charged with the dangerous operation of a motor vehicle causing death; and driving when a relevant drug is present in her blood or saliva.

She was driving her family south in a Toyota Land cruiser on October 8, 2013, when it crashed on the Bruce Highway near the village.

Her son died at the scene after being thrown 18m from the 4WD. Another so, then aged four, was found badly injured in a tree.

In a telephone link-up with the District Court Cullinane's lawyer told Judge Brendan Butler SC revealed the mother could not face a trial at the next sittings because she was 7 ½ months pregnant and could not travel.

The lawyer said Cullinane was also recently diagnosed with diabetes which complicated her pregnancy.

Judge Butler set a potential trial date for July which was not opposed by the Crown.