Singer Jessica Simpson had no problem showing off her post baby body Saturday, November 16, just four months after giving birth to Ace. 

Simpson stepped out in a diagonal striped, long sleeved, white and black, button up shirt paired with black skinny pants and pointy toed flats. She had 19-month-old Maxwell in tow as the mother-daughter duo headed to her nephew's, Bronx's fifth birthday party at The Coop in Studio City, CA. Maxwell was dressed in a brown fur vest with a cream button up shirt, blue jeans and brown printed shoes. Her light blonde hair was in pigtails at the top with the rest falling loosely at the bottom.

Simpson's fiancé, Eric Johnson, 34, also made an appearance at the bash. 

Her younger sister Ashlee and her ex-husband Fall Out Boy singer Pete Wentz hosted the party for their son. Ashlee was accompanied by her beau actor Evan Ross, who's mother Diana Ross also showed up. Wentz brought along his girlfriend Meagan Camper.

The day before, the Simpson flaunted her body during a photo shoot. She posted a picture on Instagram of her wearing a white one-piece suit. She's seen leaning by a swimming pool with her long blonde locks falling below her shoulders. Her stylist Nicole Chavez wrote, "Guess which mama I get to play dress up with today? #bts" Simpson added a ";)" when she shared the picture with her 27,000 followers.

Many seemed to like the picture as one wrote, "You are the BEST!" and others complimented her dress and shoe line.

Tags: Jessica Simpson