Janice Galloway, 58, the author of titles such as The Trick is to Keep Breathing, Foreign Parts and Blood, said concert pianist Graeme McNaught contacted her saying he had kept intimate pictures of her.
McNaught, of Mount Vernon, Glasgow, is on trial at Hamilton Sheriff Court and faces a total of 10 charges of placing Ms Galloway in a state of fear and alarm. He has denied all the charges against him.
Ms Galloway, of Uddingston, Lanarkshire, told a jury that McNaught, 54, emailed her in January 2012 and told her he planned to show the nude images at an art exhibition.
The couple were in a relationship for about six years before splitting in 1996 and the photos were taken when Ms Galloway was pregnant with their son James, now 22.
In emails shown to the court, McNaught wrote: "I have photos of you, a couple of naked pregnant shots, which I am happy to copy and hand back - it could be your page 3 moment.
"There is, if not money, artistic capital in plenty to be had from seeing them beautifully framed and hung."
Ms Galloway told the court: "He was saying 'I have photos of you with no clothes on and I will show them'. He was saying that if I didn't get in touch with him it would be a way of saying 'go ahead and do this'."
The trial before Sheriff Ray Small continues.