The 40-year-old "Modern Family" star is engaged to businessman Nicholas Loeb.
She has a 21-year-old son from a previous marriage.
"I just wanted to plan ahead," Vergara told "GMA" Wednesday about the decision to have her eggs frozen.
"My boyfriend Nicky is three years younger than me, and he's never had a son," she said. "I have my son, Manolo, so it's not an emergency for me to have another kid, but for Nicky, he's never had a baby. ... Nothing happens that naturally anymore. ... I wanted to take advantage of science. Why not?"
Asked where in the baby-planning process she is, Vergara replied: "Oh, I took them out already! They're in the refrigerator. Hopefully, they'll be fresh by the time I use them."