The Duke and Duchess of Sussex will break their silence in their first interview since quitting their roles as senior royals when they sit down with Oprah Winfrey next month.

Prince Harry and Meghan, who revealed on Sunday they are expecting their second child, announced their plans to step back from the royal family on 8 January last year.

Oprah with Meghan and Harry: A CBS Primetime Special, described as an “intimate conversation” by the US television network, will be aired on 7 March.

CBS said: “Winfrey will speak with Meghan, the Duchess of Sussex, in a wide-ranging interview, covering everything from stepping into life as a royal, marriage, motherhood, philanthropic work to how she is handling life under intense public pressure. Later, the two are joined by Prince Harry as they speak about their move to the United States and their future hopes and dreams for their expanding family.”

Winfrey is a personal friend of Meghan and attended the royal wedding in May 2018, and there was speculation at the time the couple would be interviewed by her.

Oprah Winfrey arrives for the wedding ceremony of Harry and Meghan at Windsor Castle in May 2018.

It is not known if the Sussexes informed the royal household in the UK about their plans to be interviewed, but as non-working members of the monarchy they do not have to give notice of their media commitments. Buckingham Palace declined to comment.

The news follows their Valentine’s Day announcement that their one-year-old son, Archie will be getting a new baby brother or sister. The child will be born eighth in line to the throne and become the most senior royal in the current line of succession to be born overseas, with an automatic right to US citizenship.

Harry retained his place in the line of succession despite the couple’s decision to step back from royal life and live independently in the US. But his position, and those of his children, will continue to descend the line of succession as his niece and nephews, Prince George, Princess Charlotte and Prince Louis, have children of their own.

Like Archie, the new baby Sussex will not be entitled at this stage to the style HRH – his or her royal highness – or the title prince or princess due to rules set out by George V. They are entitled to be a lord or a lady, but Harry and Meghan eschewed such a title for Archie, opting to style him plain master, with the surname Mountbatten-Windsor, and are likely to do the same for a future son, or use miss for a daughter.

The baby will be entitled to HRH and prince or princess status once the Prince of Wales – their grandfather – ascends to the throne, although it is thought unlikely that the Sussexes will opt for such a change, having forfeited their own HRH styling.

Misan Harriman, a friend of the couple, shot the black and white image released to mark their pregnancy announcement.

The photographer Misan Harriman, a friend of the couple who shot a black and white image released to mark the their pregnancy announcement, said he had captured it on an iPad remotely. The photograph shows the couple under a tree in Los Angeles, with a barefoot Harry resting his hand on Meghan’s face while she lies in his lap resting her hand on her baby bump.

Harriman, the first black male photographer to shoot a British Vogue cover– and the first to shoot its September issue – in its 105-year history, said it had been an “absolute joy” to be asked to help share the good news, especially following the loss and heartbreak the couple suffered last year when Meghan had a miscarriage.

Speculation that the duchess might be expecting a second child arose after she applied for and was granted a postponement of her privacy trial against the Mail on Sunday until the autumn for a “confidential” reason.

Any trial was averted when, on Thursday, the duchess won her high court privacy case against Associated Newspapers Ltd over the Mail on Sunday and Mail Online’s publication of extracts from a private handwritten letter she wrote to her estranged father, Thomas Markle, 76, after the judge, Lord Justice Warby, granted summary judgment in Meghan’s favour.