Samantha, 39, is expecting her fourth child in September and says that the decision came when she learned she was pregnant - long before her husband David became the new Prime Minister this week.
"This is a personal decision made when I discovered I was pregnant and one that I have been considering for some time during what has been an understandably difficult year,” she said.
In February 2009, tradgedy struck when the couple's eldest son, Ivan, passed away.
Still, Samantha will continue to have a role at Smythson, working two days a week as a consultant to the firm that she transformed into a prominent brand over the last 16 years, earning her the award of Accessories Designer of the Year in 2009.
"I will be involved in all the same areas as before, however I will not be directly responsible for them," Samantha revealed.
“I look forward to my changed role and balancing it with my new day-to-day life as well as being able to spend more time with my children.”
Samantha, who designed her latest collection in "cerulean blue" in a nod to David's party affiliation, was frequently spotted by his side during the campaign, which she said she enjoyed because of the opportunity to spend more time together.