The "Smash" star was photographed with what appeared to be a bulging baby belly on Tuesday (06Oct20), as she and musician Foster stepped out for lunch in Montecito, California, and also made a stop at a children's store, reports People.com.
McPhee was dressed in leggings and a form-fitting black top, which showed off her full figure.
The news of the 36 year old's first pregnancy emerges just over three months after she and Foster celebrated their one-year wedding anniversary.
She became Foster's fifth wife in June, 2019.
The producer is already a father-of-five to daughters Allison, Amy, Sara, Erin, and Jordan, who range in age from 50 to 34.
Katharine McPhee and David Foster have reportedly been trying to have a baby since their nuptials. While neither the couple nor their family confirm the pregnancy, two of David's daughters Erin and Sara Foster made it clear last year that they fully supported the couple to have a child.
Both daughters said they adored their stepmom, who's younger than them. "It takes a very strong, graceful person to come into a family as the fifth wife and have adult daughters who are older than her and do it in a way that really creates inclusion with the family, and she just does it effortlessly," Erin told Us Weekly. "She just makes it really easy for all of us to get along. So we're very grateful for her."