She's pregnant with her first child, but Pippa Middleton isn't adopting maternity wear just yet.

The sister of the Duchess of Cambridge, who is thought to be around four months pregnant showed just a hint of her baby bump this morning as she set off from London this morning for Harry and Meghan's big day with her husband James, reports the Daily Mail.

Pippa, 34, wore a pretty Hepburn silk floral dress from brand of the moment, The Fold which features a close-fitting bodice and pleated skirt.

READ MORE: Live: Royal Wedding 2018 - Prince Harry and Meghan Markle

The expectant mother teamed her ensemble with nude suede shoes and an elegant pale pink hat, adorned with white flowers.

She wore her brunette hair swept back in a voluminous updo and completed her look with an understated nude box clutch.

Husband James - who looked dapper in a morning suit - carried a large gift-wrapped box, no doubt containing a gift for the happy couple.

However, Pippa and James are rumoured to have been shunned for the more intimate evening do at Frogmore House, hosted by Prince Charles, to which 200 guests have been invited.

Pippa became friendly with Prince Harry during preparations for her sister's wedding to Prince William and the royal was invited to her own lavish nuptials in May 2017 - arguably the high society wedding of the year.

Harry attended the church service with his brother William and then made a 100 mile round trip to London to collect Meghan for the evening reception.

The couple chose St Mark's Church, Englefield, Berkshire, as the venue, seven miles from her family home.

She beamed with happiness as she displayed her figure in a fitted guipure lace gown by the British couturier Giles Deacon.

The couple hired a huge glass marquee, shipped from Belgium and set up in the Middletons' garden, to host their wedding breakfast and evening festivities. They drove in a green Jaguar E-Type from the Englefield Estate to the Middleton mansion.

Pippa's wedding was attended by actress and TV presenter Donna Air with her boyfriend, Pippa's brother James, while tennis superstar Roger Federer topped the guest list with his wife Mirka.

Sporty Pippa is said to be preparing to give birth "like an athlete" with a bespoke programme from her exclusive Chelsea gym.

The expectant mother was spotted walking away from the KX gym last month carrying a folder believed to be full of dietary and exercise advice, two days before new of her pregnancy broke.

KX - whose members also include Hugh Grant and Eddie Redmayne - offers a "Bespoke Package - Pregnancy Support Programme", which includes nutrition, physical therapy and exercise for nine months as well as post-natal care.

Kate was reportedly the first to be told of Pippa's pregnancy after James Matthews, and "could not have been more delighted" it has been reported.

The happy news of Pippa's pregnancy emerged after a difficult few weeks for the family following allegations of rape against her father-in-law David Matthews. He strenuously denies them, calling the claims 'untrue and scandalous'.

The 74-year-old allegedly carried out two offences between 1998 and 1999, one in Paris and another on the Caribbean island of St Barts.