The actress and husband Brady Smith, who married in 2005, confirmed that they are expecting their first child together last November.
Speaking to Pregnancy Magazine, she laughed: "[I hope my baby is] long and lean! I dream about it because my husband is 6'4''.
"I also hope the baby has his artistic side. My husband's an artist and painter, and he is so talented. I hope that comes through in our child.
"And I hope the child has my laid-back personality, because I think it will help us as parents if the child's not too high-maintenance and just loves life!"
Thiessen continued to say that she is a "wing-it kind of girl" and is trying not to stress about the impending arrival, joking that Smith is "a little more of a worrier so it will be interesting to see how [fatherhood] works for him".
However, she added: "But one of the reasons I married that guy is because I knew he was going to be great with kids."
Thiessen is due to give birth next month.