News Serena Williams's Post-Baby Underwear Selfie Game Is on Point By Brandi Fowler Brandi Fowler Instagram Website In addition to her extensive fashion, lifestyle, and beauty coverage for InStyle, Brandi has worked as a writer and editor for E! Online, a fashion and lifestyle writer for Hello! US, an editor/on-camera host for AOL, contributing writer and red carpet correspondent for Variety and Cosmopolitan, and has also served as the Hollywood correspondent for Australia's 9News' TheFIX. Her editorial features can also be found on Vitruvi, MTV News, Madame Noire, Hello Beautiful and more covering fashion, beauty, lifestyle, travel, and entertainment news. Her articles have been syndicated by the likes of Health, Marie Claire, Essence, Shape, Yahoo!, People, and more. InStyle's editorial guidelines Updated on September 28, 2017 @ 05:45PM Pin Share Tweet Email Serena Williams is not playing any games getting back into shape after delivering her baby girl. The new mom, who recently celebrated her 36th birthday, showed off her physique in a mirror selfie on Instagram Thursday, just four weeks after giving birth to little Alexis Olympia. In the snap, which had no caption (not like it needed one), Williams strikes a pose in her massive closet with a smirk in a black body-hugging top and matching boy shorts. She has one hand on her hip as she snaps a photo through the mirror. After she posted the shot, fans flooded her Instagram comments with compliments, writing things like, "Snap back game on 100!!," "You look too good girl," and dropping in plenty of fire emojis. And we have no doubt, that Williams is just getting started. Serena Williams Has Wasted No Time Getting Back in Shape The tennis superstar first showed off her progress toward getting back into peak athletic shape just two weeks post-baby with another mirror selfie that she shared on Snapchat. The one showed her posing in a pair of shorts with the caption, "Back in my jean shorts 2 weeks." Of course, Williams's speedy fitness comeback shouldn't be too big of a surprise. She kept up her exercise regimen while she was pregnant, telling The Telegraph, "I intend to keep exercising for as long as possible while pregnant. I want the baby to be healthy and for that you need a healthy life." It has certainly paid off.