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Chris Martin and Dakota Johnson sparked pregnancy rumours as an array of celebrities arrived at the singer's Malibu house for a lavish 'baby gender reveal party' on Sunday.

Screen stars Julia Roberts and Sean Penn were among the A-list guests pictured arriving at Chris' Malibu home, as well as Dakota’s parents Don Johnson and Melanie Griffith.

A source insisted to MailOnline that Dakota is not pregnant, while a representative confirmed she was hosting a birthday party, after turning 29 on October 4.  

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Expecting a baby? Chris Martin (L) and Dakota Johnson (R) sparked pregnancy rumours as an array of celebrities arrived at the singer's Malibu house for a lavish party on Sunday evening (pictured here on June 24)

Their glitzy bash comes just a week after after the 41-year-old's ex Gwyneth Paltrow tied the knot to Brad Falchuk.

Large arches of pink and blue balloons were pictured flying above the property. Moments later, blue balloons were freed into the air, presumably announcing a baby boy is on the way.

Days earlier, Iron Man actress Gwyneth, 46, wed her producer partner in front of family and friends including Robert Downey Jr., Jerry Seinfeld, Steven Spielberg, and Cameron Diaz and her husband Benji Madden in a private ceremony at a house in the Hamptons on September 29.

The couple, who embarked on a relationship in 2014, are currently ringing in their marriage with a European honeymoon.  

Star-studded: Pink and blue balloons were pictured at the 41-year-old's abode, with Sean Penn (L) and Julia Roberts (R) among the A-list attendees

Looking every inch the effortless beauty Pretty Woman actress Julia, 50, slipped her slender frame into a chic floral dress, which skimmed her lean legs.

Opting for comfort for the occasion, Julia strolled along the streets in a pair of white box-fresh trainers, and accessorised with square-framed reading glasses. 

The honey-blonde star showcased her radiant complexion with the help of light strokes of make-up, and wore her tresses in loose beach waves. 

Family affair: Dakota's mother and Hollywood royalty Melanie Griffith was also in attendance at the starry bash, as she joined Sean for a cigarette break

Baby boy? Large arches of pink and blue balloons were pictured flying above the property. Moments later, blue balloons were freed into the air, presumably announcing a baby boy is on the way

Style savvy: Looking every inch the effortless beauty Pretty Woman actress Julia, 50, slipped her slender frame into a chic floral dress, which skimmed her lean legs

Looking good: Opting for comfort for the occasion, Julia strolled along the streets in a pair of white box-fresh trainers, and accessorised with square-framed reading glasses

Julia was joined by husband Daniel Moder, who co-ordinated with his wife in a floral shirt, tied in with dark-wash pants.

Sean, 58, and Melanie, 61, appeared in high spirits as they chatted up a storm while puffing their cigarettes outside Chris' Malibu house.

The Working Girl actress exuded elegance in a white midi shirt dress, which was cinched at the waist with the help of a brown studded belt.

The blonde wore her glossy tresses into soft waves, before sweeping her hair into a relaxed updo, which revealed her striking features.

Melanie injected a hint of colour to her look with multi-coloured stripes socks, which she paired with dark brown boots.

All eyes on her: The honey-blonde star showcased her radiant complexion with the help of light strokes of make-up, and wore her tresses in loose beach waves

Loved-up: Julia was joined by husband Daniel Moder, who co-ordinated with his wife in a floral shirt, tied in with dark-wash pants

New look: The actress's appearance comes after she admitted she dropped a 'pant size' while filming her first TV series, Homecoming

Don, 68, pulled up to Chris' home in a silver sportscar as he prepared to celebrate his daughter's birthday.

The Miami Vice star was in the festive spirit as he was pictured carrying a huge medieval-inspired puppet.

Meanwhile, Dakota and Chris are famously private about their relationship, but the Fifty Shades of Grey star recently lifted the lid on their romance in an interview with Tatler magazine for its November issue, stating: 'I'm not going to talk about it. But I am very happy.' 

Dakota, 28, and the Coldplay frontman have been dating since last October after they met through mutual friends. 

Whilst Dakota and Chris might be keeping their romance out of the spotlight, the actress' parents, Melanie and Don, have both gushed about their daughter's relationship.

Industry pals: Sean, 58, and Melanie, 61, appeared in high spirits as they chatted up a storm while puffing their cigarettes outside Chris' Malibu house

Oozing glamour: The Working Girl actress exuded elegance in a white midi shirt dress, which was cinched at the waist with the help of a brown studded belt

Versatile: The blonde wore her glossy tresses into soft waves, before sweeping her hair into a relaxed updo, which revealed her striking features

Melanie, 61, said in May: 'I adore him! But she is very private about her life and I respect that.' 

In agreement, Hollywood icon Don, 68, previously gave his support to the actress' romance with the singer, admitting he thought the 'Viva La Vida' hitmaker would be 'good' for his daughter.

He said: 'He's a lovely guy. I've met him and you want your kids happy, no matter what shape it takes.

High spirits: The A-listers beamed with delight as they leaned on a white truck before heading into the party

Touch of pazzazz: Melanie injected a hint of colour to her look with multi-coloured stripes socks, which she paired with dark brown boots

Arriving in style: Don, 68, pulled up to Chris' home in a silver sportscar as he prepared to celebrate his daughter's birthday

Quirky theme: The Miami Vice star was in the festive spirit as he was pictured carrying a huge medieval-inspired puppet

'That's the goal, that's the key. He's a very talented and gifted musician. I've seen them in a concert at a small venue called the Troubadour in Los Angeles when they were first coming out and that was a memorable moment.

'I knew right then he'd be good for her. I said 'Oh you know, that man has got something going on'.'

M, it was recently claimed Dakota and Chris had gotten matching tattoos.

Dakota was spotted at the 'Suspiria' photo call at the Venice Film Festival earlier this month sporting a new inking which depicted an infinity sign crossed with two small Xs, whilst the 'Something Just Like This' singer was seen with an identical tattoo when he appeared at the launch of S.E.A Jeans in Los Angeles around the same time.