The 30-year-old actress posed for British artist Jonathan Yeo in July shortly before her due date, letting him capture her in the later stages of her pregnancy.
Jonathan, whose previous work includes paintings of Dennis Hopper and Nicole Kidman, described the portrait as a “''tribute to Sienna’s courage and self-confidence''” and praised her for stripping off for the artwork.
“I can think of many figures whose public currency in part revolves around their appearance, who would prefer to hide themselves away for nine months,” Contactmusic quoted him as saying.
“Sienna is usually so petite and a wonderful fashion clotheshorse and the fact she is transformed means it has all the more impact,” he said.
Miller, who gave birth to her first child with actor husband Tom Sturridge, first met the artist in Los Angeles, California, eight years ago and the pair have remained close friends since.
This portrait will be the sixth she has sat for in his London studio and Jonathan thinks it is the most important artwork so far. “This is the most powerful so far. There is a nervousness about it. I think it''s the anticipation of becoming a parent,” he added.