A Brisbane father has been jailed for a minimum of two-and-a-half years after he sent ultrasound images of his unborn daughter to an undercover officer to show he intended to make child pornography when she was born.

Last week, the 25-year-old man pleaded guilty in Brisbane's District Court to possessing child exploitation material and using a carriage service to access child pornography material.

The court heard the father was arrested in January 2015 by Australian Federal Police officers after a tip-off from the FBI in the United States.

The man sent an ultrasound of his unborn child and 12 images of child pornography to an undercover officer, saying he intended to make his own child pornography with his daughter.

Police found the man in possession of 6,435 images and videos of child exploitation material across three devices.

Some were of cartoons, but thousands were of actual children and babies.

The court had previously heard many of the children were showing signs of distress and pain.

Offender's statements a 'sign of moral corruption'

District Court Judge David Reid said it was the worst case of child exploitation material he had ever seen.

In sentencing, Judge Reid said the sending of the ultrasound image was not an offence but showed a "gross lack of insight".

"The fact you were prepared to make such statements is a sign of the extent of your moral corruption and your lack of insight into the nature of child abuse," he said.

He said the downloading and storing of the material was done so in a "sophisticated" way in different folders.

Judge Reid told the man that what he had described as his stated intentions with his daughter were "vile, explicit and specific".

He said he was provided a sample of the material found on the devices owned by the man.

"The material you viewed, possessed and transmitted would be seen to be revolting and upsetting to normal people," he said.

Judge Reid sentenced the man to five years' jail, with a non-parole period of two-and-a-half years.