Mayim Bialik can't stand competitive mothers.

The 42-year-old actress - who has 12-year-old son Miles and nine-year-old son Frederick with her ex-husband Michael Stone - has opened up about the time she attended a mothers' support group in a new Facebook vlog.

She shared: ''When I was a new mom, 13 years ago, I went to a 'mom's group' at a local retail store. I instantly felt out of place.

''I used cloth diapers. I didn't use pacifiers or bottles. I didn't have fancy clothes and neither did my baby. I didn't have a manicure. I mean, I barely had time to shower. How was I gonna have time to get a manicure?''

The 'Big Bang Theory' star subsequently explained that a moderator at the group was on hand to field questions from the mothers, such as ''Why does my baby want to be held so much?''.

Mayim added: ''As for me, I assumed my baby wanted to be held so much because it was a human, mammal baby. Women at this moms' group were encouraged to brag about how fast their labour was, how precocious their babies were with pooping, rolling over, sitting up, smiling.''

Mayim subsequently admitted to hating the competitive nature of the meeting.

She said: ''Everything was a competition. These were not my people. I left in tears ... Moms are so competitive! Why is that? Is it because we're just catty and combative by nature? Is it because we're bored and we have nothing better to do?''

The actress later offered a theory as to why the women were so competitive with each other.

She explained: ''I think that competition comes about because we are the first generation of women who were raised after the revolutionary turmoil of the women's movement and were the first generation who was constitutionally raised to believe that we can and should do it all.''