She is expecting a little baby sister for two-year-old son Mason next month.
And Kourtney Kardashian was proudly showing off her blossoming baby bump in all its glory on her recent Mexican holiday.
The reality show star wore the low-cut black costume with gold detailing as she joined sister Kim and her cute young son for a stroll down the beach.
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Baby on board: Kourtney Kardashian looked swell in a black low cut swimsuit with gold detailing as she celebrated her 33rd birthday in Mexico with two-year-old son Mason and sister Kim
Kourtney made sure she shielded herself from the hot sun by wearing a straw hat with black ribbon, sunglasses and a sheer wrap, while Mason sported a black and orange hat to match his aunt Kim's bikini.
Despite the Keeping up with the Kardashians star looking like she was nearly ready to pop, she clearly had enough energy to swing little Mason along the beach, with Kim's help.
However sister Kim took over much of the time, carrying Mason as she splashed around in the sea during their beach break to celebrate Kourtney's 33rd birthday.
Growing fast: Kourtney showed off her blossoming bump in the black swimming costume with gold detail
A swinging good time: Kourtney looked in good spirits as she and sister Kim swung two-year-old Mason along the sands
Kourtney and long term boyfriend Scott Disick announced they are expecting a baby girl back in February after announcing the pregnancy last year.
'We feel so blessed to be having a little girl and to be able to share this new experience with Mason,' Kourtney told E!
However, it hasn't been all plain sailing for the oldest Kardashian, who recently admitted she has suffered from panic attacks and claustrophobia during her pregnancy.
Hats off! Kourtney shielded herself from the son in a straw hat with black ribbon and a sheer patterned wrap while Mason wore a black and orange hat
Not all plain sailing: Although Kourtney looks in good spirits, she recently admitted suffering claustrophobia during her pregnancy
'I have been claustrophobic just recently in my third trimester of my pregnancy,' she wrote on her Celebuzz blog, before describing an experience at LAX airport last month.
'I had a small panic attack in customs when they stopped everyone in a tunnel. Looking behind me all I could see was people and in front of me tons of people and I couldn't even tell where the tunnel ended,' she recalled.
'I had to just run to the front of the line, because I literally couldn't breathe. It's a horrible feeling and I'm hoping that it goes away after my pregnancy. I hate that feeling of being trapped with no control. Ahhh deep breath!'
Sister act: Kim helped her pregnant older sister look after Mason during their sunshine break
Meanwhile, Kourtney's boyfriend Scott was busy showing off his new wheels in Calabasas, California today.
The 28-year-old reality star looked proud of the shiny chrome-plated Audi R8 as he ran errands in the Los Angeles sunshine.
An Audi R8 costs around £140,000 and Disick would have spent between £30,000 and £40,000 to have the chrome wrap added.
Mirror mirror: Scott Disick looked particularly proud of his new chrome-plated Audi R8 as he ran errands in Calabasas today
Dapper: Scott wore shorts and a polo shirt and carried a briefcase-style holdall in the sunshine
As well as the wrap, he also splashed out on 20" gloss black Freddo-M wheels from the Monoleggera Series, which was done by Calabasas Luxury Motorcars.
And her wheels are the envy of the whole family, with Kim already taking a turn behind the wheel.
She uploaded several photos of her posing in the car on Twitter last week, writing: 'Scott's sick new car! Chrome!'
She joked: 'Who needs a mirror when I'm driving @scottdisick's car!?!'
The comment was then retweeeted by Scott, who agreed: 'No need.'
Batmobile: The Kardashian family tweeted photographs of Scott's shiny new motor last week