Spelling, 43, announced Thursday night on Twitter the spouses of 10 years have welcomed their fifth child into the world.
"We are so excited to announce the birth of the newest member of the McDermott family! Please join us in welcoming Beau Dean McDermott," Spelling captioned a black-and-white photo of the baby holding McDermott's hand on Thursday night.
Beau Dean was born at 1:48PM on Thursday, weighing five pounds and 12 ounces, Peoplereported, and he measured 18.5 inches long.
"We are over the moon in love with baby Beau. He is a true blessing and his brothers and sisters were overjoyed to meet him! We are all truly grateful for our big beautiful and healthy family," Spelling, who most recently starred on True Tori, told the magazine.
The new baby boy joins four older siblings -- Finn, 4, Hattie, 5, Stella, 8, and Liam, 9. McDermott, 50, also has an 18-year-old son Jack from his previous marriage.
Spelling reportedly celebrated her baby shower at Hotel Bel-Air in February hosted by her mom, Candy Spelling, and celebrity event designer Mindy Weiss.
Spelling and the former Chopped Canada host revealed they were expecting a son in December 2016 by sharing a video showing off their blue-decorated Christmas tree.
"It was a total surprise," Spelling told People at the time. "But we always wanted a big family. I'm really excited... This baby happened at the best time. Nothing is ever perfect, but I'm so madly in love with my husband and with our kids. The idea of adding to that is such a blessing."
Spelling laughed about how McDermott thought they were in the clear once Finn was out of diapers. With the rest of her children in school and a new baby on the way, the parents felt like they were starting over.
McDermott had told the magazine Beau was "a miracle baby" because it was a longshot for Spelling to get pregnant again after suffering from placenta previa -- a condition in which the placenta blocks the cervix -- while carrying Finn.
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Spelling felt very lucky that was not the cast this time around, as her life would have "potentially [been] in danger."