Oh, so that's where she gets it from! A new report claims the ~mystery~ behind Kim Kardashian's enviable breast region has been revealed — and she has fillers to thank for her two perfect boobs! While the reality star has dropped a ton of weight ever since welcoming her son, Saint West, she can credit "injectable fillers" for giving her such "pumped-up cleavage."

“There’s one [filler] designed for body-shaping that Kim is using,” a source told OK!, adding, that “it’s the reason her breasts are so full right now, despite the weight she’s lost. Kim’s getting small doses regularly so it’s not an overnight change. Once she achieves the maximum effect, she’ll likely give it a rest.”

MORE: Saint West Is Already Talking — Check out His Adorable Little Voice!

The Keeping Up With the Kardashians star was candid in the past about her dramatic body changes and health issues during her pregnancies with both her daughter, North, and son, Saint — so she and her husband, Kanye West, have allegedly decided to take the surrogacy route for their third child. Us Weekly reported last week that the surrogate is three months along.

Scroll through the gallery to see more photos of Kim's sexy body!