Kristin Cavallari has a pretty good reason for missing her 10-year high school reunion.

She and husband Jay Cutler welcomed their third child, a baby girl, on Monday, the reality star turned designer announced last week.

On Sunday, the Laguna Beach alum showed off the new addition to the Cutler family, Saylor James, in an adorable Instagram snap.

“Really sad about missing my 10 year high school reunion last night … so many people I wanted to see … but at least I have a good excuse,” Cavallari, 28, captioned the pic.

Kristin Cavallari and Saylor James Cutler

Courtesy Kristin Cavallari

Cavallari and Cutler, quarterback for the Chicago Bears, announced the pregnancy in May. The two are already parents to two sons, Camden Jack, 3, and Jaxon Wyatt, 18 months.

Cavallari said in August that she and Cutler, 32, were grappling with having three children or four — although there are no immediate plans to become a family of six.

“Before we had children, Jay and I both wanted four, and now we’re thinking three, but we’re just going to have to see how it goes,” she told Michigan Avenue magazine.

“Right now the last thing on my mind is having another baby, but it is a ton of fun.”

— Char Adams