Credit: Jamie McCarthy/; FameFlynet

Just four months after giving birth, Jessica Alba looked absolutely flawless in a teeny bikini while vacationing in Cabo San Lucas, Mexico on Monday.

The 30-year-old mom of Haven, four months, and Honor, 3, even inspired one pregnant star with her post-baby physique: Jessica Simpson

"New goal: look like Jessica Alba after baby," Simpson, 31, tweeted Tuesday. "Job well done, lady!" 

Alba, who told Us Weekly she didn't go "too crazy" dropping her baby weight, was flattered. "OMG! You're so sweet!" she wrote in response to the Fashion Star mentor. "Thanks, hon!" 

The Spy Kids 4 actress secret to shedding the pounds? "I didn't gain as much weight with my second pregnancy, so I think that made a really big difference," she said.

"I did prenatal yoga up until the very end," she added. "I just made healthier choices. I started working out and not going too crazy, but I did what was safe and what the doctor approved."

Simpson, who is expecting her first child with fiance Eric Johnson, is reportedly in talks with a post-pregnancy $4 million Weight Watchers deal.