Pippa Middleton joined her family at Prince Louis' christening on Monday afternoon, and the Duchess of Cambridge's younger sister was sporting another pretty maternity look.

Pippa, who is expecting her first child with her husband, James Matthews, wore a baby blue shirt dress custom-made by Mayfair-based designer Alessandra Rich, according to blogger Middleton Maven, for her nephew's baptism at The Chapel Royal, St James's Palace.

Pippa Middletonpinterest
Getty Images

She accessorised the design with a matching hat, an ivory clutch bag and satin Jimmy Choo pumps (similar style available here) and gave royal fans another glimpse of her adorable look on exiting the service.

Pippa with her husband, James Matthewspinterest
Getty Images
Pippa with her husband, James Matthews

She attended the royal celebrations alongside her parents, Carole and Michael Middleton, and brother, James Middleton. The royal baby's six godparents and their spouses were also in attendance for the special ceremony.

instagramView full post on Instagram

Pippa's appearance comes a few days after she attended Wimbledon, where she was spotted wearing a bespoke white Broderie Anglaise Bergman dress by designer Anna Mason. Earlier this month, the mum-to-be opened up about her love of fitness and how she continues to play tennis while expecting.

'I've been a tennis fan since childhood, as player and spectator, and have been keen to continue playing safely throughout pregnancy,' Pippa wrote in a piece for Waitrose Weekend.

In a previous fitness article for the magazine, Pippa noted that she hasn't suffered morning sickness, unlike Kate, who experienced severe morning sickness while pregnant with Prince Louis.

'I was lucky to pass the 12-week [mark] without suffering from morning sickness,' she wrote. 'That meant I was able to carry on as normal and continue most of my sports with better knowledge and, more importantly, professionals to learn from.'