Sienna Miller, 42, looks incredible in a purple bikini as she holidays with boyfriend Oli Green, 27, in Costa Rica -  three months after welcoming their first child together

Sienna Miller and her boyfriend Oli Green have been pictured soaking up the sun on a getaway to Costa Rica three months after welcoming their first child together.

The actress, 42, who also mother to her daughter Marlowe, 10, looked sensational as she strolled along the beach in a purple bikini with Oli, 27.

It was announced in January that the couple had welcomed a baby girl - whose name is not known - almost two years after they were first romantically linked.

Just months after their daughter's arrival, Sienna looked glowing in vibrant swimwear during a walk along the shoreline with her actor boyfriend.

The bare-faced beauty went for a natural look by ditching make-up and wearing her blonde locks loose following a dip in the sea.

Sienna Miller and her boyfriend Oli Green have been pictured soaking up the sun on a getaway to Costa Rica three months after welcoming their first child together

The actress, 42, who also mother to her daughter Marlowe, 10, looked sensational as she strolled along the beach in a purple bikini with Oli, 27

It was announced in January that the couple had welcomed a baby girl - whose name is not known - almost two years after they were first romantically linked 

The couple put on a loved-up display as they walked hand-in-hand, talking and laughing as they spent time together on the beach.

Shirtless Oli sported just a pair of swimming shorts, while they were both wearing matching gold chain necklaces. 

Sienna's pregnancy was revealed during a beach holiday in August where she stepped out sporting a bump.

In December Sienna covered Vogue as she spoke for the first time about her pregnancy and revealed she was having a girl. 

In incredible photos taken to accompany the interview she displayed her bare bump alongside both Marlowe and boyfriend Oli.

Sienna spoke candidly about her pregnancy and how it had been 'unplanned', but admitted she feels 'more psychologically prepared' than with her first born.

During the rare interview, Sienna said that Marlowe has been angling for a sibling for some time. Sienna shares Marlowe with her ex-boyfriend Tom Sturridge.

Sienna also said she'd been fighting her own prejudices about being an older mother and has to learn to stop making a joke out of it.

She told the publication: 'I'd love to get to a point where I didn't feel the need to make a joke of my being older and having a baby, to show I'm in on the joke.' 

Just months after their daughter's arrival, Sienna looked glowing as she sported the vibrant swimwear during a walk along the shoreline with her boyfriend

The bare-faced beauty went for a natural look by ditching make-up and wearing her blonde locks loose following a dip in the sea

And in a video she filmed with Vogue, Sienna revealed that the pregnancy was an unplanned one.

She revealed: 'I was very fortunate. I wasn't necessarily trying to get pregnant. This happened as a total surprise and biologically was something I was able to do.' 

Sienna went on to further address the stigma around pregnancy as an older woman as she has fought her own prejudices around the subject.  

She added: 'I think people are comfortable with a way of living that has existed for many years, which is very misogynistic and patriarchal.

'Like me being the older woman in a partnership with a younger person or being pregnant over 40 and that that's irresponsible and poor child and it's such double standards.'

On what is different this time around, she said: 'I have expectations where I had none before. I feel much more psychologically prepared than I was with Marlowe. 

'It was quite a shock, the reality. I hadn't given it the thought, I guess you can't prepare for it. In my mind I imagine it's going to be the loveliest, but I think I've forgotten.'

During the interview, Sienna, who was 31 weeks along at the time, detailed the difference in her mentality surrounding her birth plans between her first and second children.

Oli went shirtless and sported just a pair of swimming trunks

The couple were both wearing matching gold chain necklaces

Sienna's pregnancy was first revealed when she was pictured with a baby bump in August

She admitted she was 'feeling' pregnant in her 'head and face' and noticed she was moving around with a 'slight waddle' - as well as needing to go to the toilet around '18 times a night'.

Sienna said that with Marlowe, she had her heart set on a 'natural' birth, with her sister Savannah, 44, (who had delivered several times at home) as her doula. 

But instead, she was induced at the hospital and 27 hours of gruelling labour followed. 

She added: 'It was like a horrible trick of the universe. I was like, This can't be what my sister felt at home in her birthing pool.'

Sienna was given an emergency C-section, which she called a destabilizing experience. She said: 'It was so essential in my mind that I got it 'right.' And so emblematic of the kind of mother I would be that I didn't. 

'But I know in retrospect that was just the demons of new motherhood. This time, she says, 'I just don't think I'll put that pressure on myself'.'

Sienna welcomed Marlowe with Tom, who she now has a close friendship and co-parenting relationship with.

Tom is now dating her friend Alexa Chung, and she said of the dynamic: '

Sienna's pregnancy was revealed during a beach holiday in August where she stepped out sporting a bump

'Alexa she is much more generous to because she is exquisitely dressed and not her actual mother. It's very loving and cosy and great.'

Sienna said she still wants to try for a natural birth, and she's recently switched to a doctor who is aligned with that viewpoint. 

The actress, who was previously in a long-term relationship with Jude Law, 50,  confirmed she was expecting her second child during a beach holiday in August. 

Sienna and actor Oli have been dating since 2021 and he is 15 years her junior. 

Opening up on their age gap for the first time with Vogue, Sienna said: 'I would imagine it would be complicated for anyone to get their head around, but there's been nothing but love and joy.' 

'I don't think you can legislate on matters of the heart. I certainly have never been able to.' 

And on the issue that he may someday want someone younger, she simply said: 'For Oli, it is real that I might want to be with someone older.' 

Later on in the interview, as Oli celebrated his 27th birthday, she joked about being relieved to not be dating a 26 year old anymore.  

The two were first romantically linked in early 2022 when they were spotted together in New York - and Sienna has now revealed they met at a Halloween party thrown by a mutual friend. 

Sienna is pictured at her baby shower late last year, where everything was themed pink for her girl

Sienna looked incredible as she showed off her bump at the Vogue World Event in September

Sienna spoke about her pregnancy in the January issue of Vogue magazine 

Although they kissed when they first met, Sienna said that she then 'retreated', believing the relationship wouldn't 'go anywhere'.

However dogged determination from Oli eventually persuaded her to go out for a drink in New York - and Sienna brought along a wing-woman pal in the form of Emily Blunt. 

Emily has said: 'When I got there, it was so beautiful between them. I just gave her a hug and went 'I'm going to slip away'.

'I see so much of her in him, in that free-spirited curious guileless thing that he has.' 

Oli is also an actor in the latest series of The Crown as Rupert Finch, a university friend of the Prince and Princess of Wales while they were at St Andrews.

As for THAT divisive two-piece Schiaparelli ensemble she wore at Vogue World in September in London, Sienna said: 'I was nervous about the idea of it, but once I had it on, everything else felt boring. 

'I was like, I'll have that photo for the rest of my baby's life. It's kind of fascinating to fight your own prejudice against yourself. I'm constantly doing that.'

Although the Vogue interview was the first time Sienna officially said she was having a baby girl, she previously hinted at it during her very lavish baby shower, where she was joined by family and celebrity friends.

Sienna showed off her blossoming bump in a baby pink dress, accompanied by a flower crown with differing hues of blush, again hinting towards a baby girl. 

The actress previously admitted to freezing her eggs after turning 40 because she feared the prospect of having no more children.

She told ELLE: 'Biology is incredibly cruel on women in that decade – that's the headline, or it certainly was for me.

'Then I got to 40 and I froze some eggs. Having been really focused on the need to have another baby, I'm just like, if it happens, it happens. That kind of existential threat has dissipated.'

Sienna is also mother to daughter Marlowe whom she has with her ex Tom Sturridge (pictured together in 2015). The pair are still very close

Prior to her relationship with Tom, Sienna was engaged to fellow actor Jude Law in 2004 after he popped the question on Christmas Day (pictured in 2010)