"Some bellies took 15 minutes to paint and some bellies took two or three hours to paint," Blakely tells ET. "All of them were eight or nine months pregnant and actually a lot of them we painted on the due date. There were a lot of contractions going on."
Some of the moms featured in the book include Kate Winslet, Alyssa Milano, Milla Jovovich, Savannah Guthrie and Elsa Pataky.
"Kate did Earth on her own belly," Blakely recalls. "She was so particular about England being well represented that she actually grabbed the paintbrush and started painting her own belly."