Mom-to-be Pippa Middleton was spotted on another casual bike ride in London, but this time she forwent the breezy, floral dresses and went for a chic dark look. The Duchess of Cambridge's younger sister wore a black long-sleeve dress with a white Peter Pan collar, reminiscent of Wednesday Addams' signature look in The Addams Family. (Pigtail braids not included.)

The frock is believed to be from ASOS, but it's already sold out. Middleton finished off the outfit with sunglasses, white sneakers, and a black backpack, which she kept in her bike basket.

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Pippa is expecting her first child with husband James Matthews, and is reportedly due in October. Princess Eugenie is set to marry Jack Brooksbank the same month, so it's possible Kate Middleton could miss the wedding to be by her sister's side, says Closer.

Pippa has been documenting her pregnancy fitness journey through columns written for Waitrose Weekend. "Sport and exercise has always formed part of my daily life, from gym sessions to weekend runs, ambles or training for an event. Fitness gives me energy and helps clear my mind," she wrote in one column.

"I love the endorphins and the buzz factor that exercise gives," she continued. "When I learned the happy news that I was pregnant I realized I needed to adjust my normal 4 to 5-day-a-week routine and find a way of continuing my exercise safely throughout the three trimesters. So, the journey of pregnancy fitness began."

Besides the frequent bike rides, Pippa has stayed active by playing tennis. "I've been a tennis fan since childhood, as a player and spectator, and have been keen to continue playing safely through pregnancy."

A Look Back at Pippa Middleton's Chic Maternity Style

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