Yothers, who is best-known for playing Jennifer Keaton on the 1980s sit-com "Family Ties," also recently won the U.S. reality TV series "Celebrity Fit Club."
She and her husband, Robert Kaiser, welcomed Jake Kaiser at 6:08 a.m. Monday at an Orange County hospital, People.com reported.
This is the fourth child for the family whose last addition, Lilly, turns two next month. Kaiser has two sons from a previous marriage.
Even at five months pregnant, Yothers weighed less than before her appearance on "Fit Club 4."
"I was triple this size when I was pregnant with Lilly, since I only worked out my hand and mouth," she told People.
She offered this bit of advice to those who want to drop some weight, "Find a cookie you don't like."