A US magazine ran the bikini pictures alongside the headline: "First Bump Pics, World Exclusive."
While a friend of the couple reportedly told InTouch Weekly: "She's pregnant. She and Justin are ecstatic. Jen has wanted to have a baby with Justin for years.
However, her rep denied she's expecting: "It is just another total fabrication. Jennifer is not pregnant."
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Her bearded husband went for a rough and ready look in a white sleeveless top, black jeans and matching cap. Swoon.
Jen's estranged mother, Nancy Dow, died recently aged 79 after suffering a long illness.
In a statement, the star said: "It is with great sadness that my brother John and I announce the passing of our Mother Nancy Dow. She was 79 years old and passed peacefully surrounded by family and friends after enduring a long illness.
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Jennifer and her mother had a tricky relationship, and the star previously admitted her mum was "very critical" of her.
Nancy didn't help the situation when she published a tell-all book, From Mother and Daughter to Friends: A Memoir, about Jennifer's life in 2009.