Mrs Cameron is due to give birth in September
Samantha Cameron has announced she is stepping down from her role as creative director of luxury stationers Smythson.
The new prime minister's wife, who is five months pregnant, said she would instead work as a creative consultant for the company two days a week.
Mrs Cameron, 38, said it was a decision she had been "considering for some time during what has been an understandably difficult year".
The Camerons already have two other children, aged six and four.
Their older son Ivan, who had cerebral palsy and epilepsy, died at the age of six last year.
Announcing her decision on Thursday, Mrs Cameron said: "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.
"As a creative consultant working two days a week I will be involved in all the same areas as before, however I will not be directly responsible for them.
"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."
Mrs Cameron has worked for Smythson, which is based in London's Bond Street, for 14 years. The company also sells luxury leather goods, and the £1,000 "Nancy" bag is named after her daughter.
She had been working for four days a week, but cut down to two days during the election campaign to join her husband on the trail.