The mum-to-be kept her baby bump wrapped up in warm in a long black coat, with floral leggings and comfortable Nike trainers.
Wearing stylish black-framed sunglasses, Liv looked happy and relaxed as she walked around the Soho neighbourhood.
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The 37-year-old actress revealed she was expecting her second child early in September, with sources confirming that the star is "delighted" by the news and that she was "really trying for another baby".
She is currently dating British sports agent Dave Gardener and the pair first went public with their relationship over the summer.
Liv is already a mum to nine-year-old Milo with her ex-husband, British musician Royston Langdon.
The Lord of the Rings actress and Dave have been pictured together out and about in the last four months after being introduced by mutual friend Kate Moss. In July they joined the supermodel and her husband Jamie Hince on holiday in Spain.
has made no secret of her desire to have more children. In a recent interview with the Sunday Telegraph's Seven magazine, she said, "I'm 100 per cent planning on it.
"If the stork could just drop it off on my roof, I'd be so happy – I'd have, like, 20."
The actress is less certain about tying the knot for a second time, though, explaining that her perception of a fairytale ending has changed over time.
"That's something interesting that happens in your thirties. You're not in the stage anymore of princes and happily ever after. It's a different stage of acceptance and realisation about the realities of love and relationships. Forever is a long time."