The 43-year-old actress and reality star discussed the possibility in an interview with People after welcoming her fifth, son Beau Dean, with McDermott in March.
"All my kids have their little pair, so I could be open to one more," Spelling told the magazine. "Hey, if people call you the Brady Bunch, you have to complete the Brady Bunch."
"I forgot how much I loved being pregnant," she added. "I love the connection. You are never alone."
Spelling and McDermott are also parents to 10-year-old son Liam, 8-year-old daughter Stella, 5-year-old daughter Hattie and 4-year-old son Finn. The actress gave birth to Beau on March 2.
"We are so excited to announce the birth of the newest member of the McDermott family!" she tweeted the same day. "Please join us in welcoming Beau Dean McDermott."
"We are over the moon in love with baby Beau," the star added in a statement. "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, an actress known for Beverly Hills, 90210, married McDermott in 2006. The couple starred on the reality series True Tori after McDermott admitted in 2014 to cheating.
"Rebuilding our marriage took time," Spelling told People. "And now, having a new baby, it makes sense. It's like a new baby in a new relationship."
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