Battle of the behinds! Pregnant Kim Kardashian bumps into bootylicious pal Serena Williams in London… as the tennis ace strokes her growing baby bump

Her second pregnancy has so far led to little change in her wardrobe.

And Kim Kardashian chose another revealing look on Friday before bumping into her old friend Serena Williams who couldn't resist touching the star's growing belly.

The bootylicious ladies embraced on the street outside Harrods and Kim placed her hands on her hips as the World Number One tennis player rubbed her baby bump.

 Shape shifters: Kim Kardashian bumped into her old friend Serena Williams who couldn't resist touching the star's tummy

The Keeping Up With the Kardashians star, 34, who is expecting a baby boy later this year, dressed for the London heat in her plunging outfit.

She showed plenty of cleavage in a low-cut black top and ruffled skirt.

In stark contrast Serena embraced the sporty look in a white and purple Nike tank paired with skin-tight grey leggings and trainers just days before the start of Wimbledon.

 Growing belly: Kim seemed to be touched at the middle as the tennis ace paid reference to her bump

 Bump watch: Kim placed her hands on her hips as the World Number One tennis player rubbed her tummy

 Close friends: Kim and Serena joked and laughed together as they chatted outside Harrods

Gentle: Serena carefully ran her hand over the Keeping Up with the Kardashians' star's belly

Figure hugging: Both Serena and Kim wore form-fitting outfits which showed off their curves

 Old friends: They embraced on the street outside Harrods in London

 Sporty look: Serena wore a white and purple Nike tank and dark grey leggings