Thousands have commented on a photograph posted on Twitter by Kardashian of herself with a friend, reported Daily Mail.
Many of the social networking site users made cruel remarks about the 32-year-old socialite's weight and criticised her for being in a club while pregnant.
One user labelled her "no fit mother" while another called her "fat", adding "lose some weight". Kim's boyfriend West revealed her pregnancy at a concert\ , and the abuse started hours after the picture went online showing her at 1Oak nightclub in Las Vegas with her friend and fellow reality TV star Brittny Gastineau.
The criticism has now sparked a backlash with fans and anti-trolling campaigners reacting angrily, leaving their own messages of support and describing the 'haters' as 'losers' and 'lowlifes'.
Kim is the latest celebrity with a baby to have been targeted by internet trolls in recent months. In October soul star Adele was targeted after the birth of her baby boy was announced.
Her news went up on Twitter and within minutes shocking tweets threatening to kill both Adele and her son had been posted.
Similarly, 'X Factor' judge Gary Barlow, 41, was taunted online after his daughter was stillborn in August.