Sims announced that she was pregnant on her personal website in September, and on Monday she wrote about how thrilled she was to be expecting a baby girl.
"We couldn't be more excited," Sims wrote on her site. "I can't wait to meet our baby girl and I just know that Brooks is going to be the very best big brother ever. Two kids under three … here we GO!"
Sims and Stuber, who got married in September 2011, welcomed their son Brooks in June 2012.
"We are over the moon and can't wait until our precious little girl arrives," Sims wrote. "Now the question is, what do you think we'll name her?"