What happens in Vegas stays in Vegas.

A photo posted by Kourtney Kardashian (@kourtneykardash) on Apr 19, 2015 at 11:17am PDT

What happens in Vegas…? Though she traveled to Las Vegas to ring in her 36th birthday on April 18, Kourtney Kardashian still took the time to fulfill her motherly duties. 

On Sunday, April 19, the mother of three posted a shot of herself lounging on a kitchen island with breast pumps hooked up to her chest on Instagram with the caption, "What happens in Vegas stays in Vegas." 

About last night.

A photo posted by Kourtney Kardashian (@kourtneykardash) on Apr 19, 2015 at 10:36am PDT

The eldest child of the Kardashian-Jenner clan welcomed son Reign Aston Disick in December 2014 with her longtime partner Scott Disick (the couple already shares son Mason, 5, and daughter Penelope, 2. 

Seasoned party promoter Disick, 31, travelled with Kardashian to Vegas for her big bash, but an eyewitness tells Us Weekly that the known party boy drank water all night. 

Goodnight vegas

A photo posted by Scott Disick (@letthelordbewithyou) on Apr 19, 2015 at 2:42am PDT

To ring in another year, the reality star wore a black Wolford bodysuit, Balmain skirt, and Tom Ford lace up heels. She brought giant cutout heads of herself and Disick to the 1Oak nightclub. 

Naturally, her tight-knit family all wished her a happy birthday, even though none of them made it out to Vegas to celebrate. Kourtney even Instagrammed her younger sister Khloe Kardashian's card, which read, "To the best, finest, grooviest, most on fleek, bad ass, MILF, bootyliscious, sister in the world!!! You are the ying to my yang, Siegfried to my Roy, Sonny to my Cher and the Ricky to my Lucy! I love you more than I could ever ask for!"

Best birthday card ever from my Koko Loco @khloekardashian ????

A photo posted by Kourtney Kardashian (@kourtneykardash) on Apr 18, 2015 at 11:39am PDT