Mila Kunis  stepped out in Los Angeles yesterday in a formfitting black tank that showed off her adorable baby bump. The actress has become a regular at prenatal yoga classes , even attending one on her 31st birthday  last week. She recently spoke out about the late Robin Williams , whom she recently worked with on The Angriest Man in Brooklyn, saying that he reminded her to step back and enjoy  the special moments she has experienced. It appears that the actress may be taking his advice — it seems like she's been having fun  during her pregnancy while spending plenty of time with her fiancé , Ashton Kutcher . He recently took the Ice Bucket Challenge  with his and Mila's That '70s Show costar Wilmer Valderrama .