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Britney Spears opens up about lip injections, Kim Kardashian and pregnancy sex in the January issue of InStyle.

The pop star reveals that she’s gotten some assistance from renowned Beverly Hills plastic surgeon Dr. Raj Kanodia.

“A doctor I see, Dr. Kanodia, does fun stuff to me sometimes — I’ve had lip injections before,” Spears tells the magazine. “He has this peptide-based face-care product; it’s green and slimy, and you mix it together and put it on your face. It does wonders. You leave it on overnight.”

Sounds good.

That said, Spears thinks “it’s cruel how the world puts so much emphasis on our looks.”

She refers to Kardashian’s harsh treatment by the press during her pregnancy.

“I see Kim and what she went through when she was pregnant — the tabloids were so mean to her because she was big,” says Spears. “At one point in the show she was upset and said something like, ‘I would be lying if I said that the criticism from the paparazzi while I’ve been pregnant hasn’t taken a toll on me.’”

“And I was like, ‘Bless her heart,’ because I remember that time,” the singer tells InStyle.

Spears adds, “First of all, you are already emotional, and then the paparazzi are taking pictures of you pregnant. That should be the time when your body is the most treasured.”

“I loved being pregnant for so many reasons,” she says. “Not to mention the sex is awesome then.”

Good to know.