Megan Fox and More Celeb Moms Battle the Baby Bulge

Nov. 20, 2012— -- intro: New mom Megan Fox is getting back to her title as the World's Sexiest Woman.

Just two months after giving birth to her son Noah, whose father is actor Brian Austin Green, Fox stepped out Monday looking svelte and healthy. The "Transformers" actress attended a screening of her new film "This Is 40" in Beverly Hills, wearing a black t-shirt, dark skinny jeans, a navy blue blazer and black pumps. The new mom looked like she may be close to her pre-baby body.

Fox kept her pregnancy under wraps until photos of her with a bulging belly revealed that she was expecting. The "Jennifer's Body" actress gave birth Sept. 27 and revealed the news on her Facebook Oct. 17.

Fox dropped her pregnancy pounds incredibly fast, but that's not true for all moms in Hollywood. Check out who else is working to get back to their pre-baby bodies:

quicklist: 1title: Vanessa Lacheytext: It didn't take long for Vanessa Lachey to get her pre-baby body back. Just four weeks after giving birth, the former MTV host showed off a mucher slimmer figure.

In the beginning of October, the new mom stepped out for the first time since giving birth to son Camden John , whose dad is former 98 Degrees frontman Nick Lachey. The glowing 31-year-old looked like she was back to her pre-baby figure as she headed out to cheer on brother-in-law Drew Lachey in "Dancing With the Stars: All Stars."media: 17436923

quicklist: 2title: Jessica Simpsontext: As the new face of Weight Watchers, Jessica Simpson hasn't tried to hide her body since giving birth to daughter Maxwell Drew in May. The new mom officially unveiled her post-baby body on the premiere of Katie Couric's talk show Sept.10, saying that losing her pregnancy weight has been a "lot of pressure" and a "challenge."

"During pregnancy, I didn't really think about it," she said about her weight gain. "I thought my doctors were telling me that it was just a lot of water and whenever my water broke my whole entire stomach would go down but that did not happen. All the weight did not come out with the baby."

On "Katie," the 32-year-old singer and reality TV personality revealed that she's already lost more than 40 pounds. She previously said she weighed 170 pounds when she posed nude and pregnant for the April issue of Elle magazine.

Simpson is trying to keep the weight off by walking with her new baby girl -- her goal is to walk 14,000 steps a day -- but she knows diet makes a difference too.

"I feel like what made me eat more is my hormones and breastfeeding. I've never wanted chocolate more in my life," she said. "I've had to really stay focused and focus on my diet and concentrate on what I'm putting in my body."media: 17437098

quicklist: 3title: Hilary Dufftext: Hilary Duff is working hard to drop her pregnancy pounds and insists she's doing it the healthy way. The former teen star turned author is routinely spotted at the gym and reportedly takes Pilates classes to tone up. Duff, 25, told Us Weekly that every time she feels defeated, she looks at her new son, Luca Cruz Comrie, and realizes it's all worth it.

"I'm fine with it," she said about her body. "Obviously, I'm not where I want to be eventually, but I'm working hard and I'm doing everything I can to lose the weight the right way. I'm breast-feeding, so you have to be careful and not do anything too drastic."media: 17438174

quicklist: 4title: Adriana Limatext: Working up a killer sweat is part of Adriana Lima's job as she readies for the annual Victoria's Secret fashion show. The 31-year-old model, who gave birth Sept. 12, was spotted in Miami this week taking off her sneakers and dripping in sweat. Later that day she tweeted a photo of herself with slicked back hair and a sweat soaked shirt, writing, "Just finish workout;)."

Lima is a lover of boxing, jump rope and high intensity cardio. After having her first child in 2010, the model told Us Weekly she worked out every day, sometimes twice a day, and that dropping the weight "was easy." media: 17437455

quicklist: 5title: Kourtney Kardashiantext: Kourtney Kardashian has managed to shed pounds and look chic since giving birth to her daughter Penelope in July. The reality star has been spotted around Miami, Fla., rocking stilettos, skinny jeans and what appear to be her pre-pregnancy dresses.

She's working for it: photogs have snapped Kardashian running and doing squats on the beach. But the 33-year-old mom of two, who gained 45 pounds during her pregnancy, said she doesn't want to do anything drastic. After giving birth to her first child, Mason, in Dec. 2009, Kardashian revealed that she went too far by trying to drop the baby weight fast. On a 2010 episode of "Kourtney & Khloe take Miami," Kardashian passed out during a run on the beach. media: 17437414