The baby girl was born at 8:16 a.m. on Monday, August 21, in Newport Beach, California. She weighed in at 7 pounds, 12 ounces, and measured 21 inches long.
"We are so unbelievably in love!" the new parents told ET. "We are so excited to start this new chapter of our lives and never thought we could love someone so much."
Delilah is already a "daddy's girl," the couple gushed, adding that Wahler, 30, "loves to swaddle and cuddle with her."
The Laguna Beach alum and Slack married at Calamigos Ranch in Malibu in October 2013. They announced her pregnancy in February, joining fellow MTV stars Whitney Port and Lauren Conrad, both of whom welcomed babies in July.
In fact, Wahler and Slack discovered that they were expecting the same day that his ex-girlfriend Conrad, 31, announced her pregnancy. "This is so funny — so we found out the morning of New Year's Day [that I was pregnant]," Ashley exclusively told Us Weekly in February. "Then I saw that Lauren was pregnant that same day, that she came out saying she was pregnant, and I was laughing, because I'm like, 'Oh, my gosh, that's so funny that it just happened all at the same time."
Waller added, "Literally, we texted somebody saying, 'Oh, my God, we're pregnant!' and they sent us the thing about Lauren ... I was like, 'So awkward.'"
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