While promoting her book, The Bump Class, at the Henley Literary Festival, Marina said she was stunned by some of the women's attitudes, with some even telling her she was a 'failure', and that it was a 'shame' that she had two C sections.
'People love to judge, they love to be smug about their own births. I don't think that's fair,' she said.
'I remember someone saying to me "what a shame". I said, "what do you mean a shame? I have a baby who is alive, I'm so grateful to the medical profession for giving me this".
'But people love to judge, they love to be smug about their own births. I don't think that's fair.'
Marina has two children, Iona and Ludo, with husband Ben, who also spoke at the event about the judgement his wife has faced.
'I know that we have had people say to us, "did we not feel robbed" or that you [Marina] were a slight failure.'
When asked why she thought women were being so condescending, Marina put it down to competitiveness.
'I think there is an innate competition,' she said.
'It is a bit like all girls schools, you know when you get a lot of girls in an environment together, with maybe a bit more time on their hands, it can turn into a really bitchy situation and I wonder if that's just girls overthinking it.'
Marina runs antenatal courses with her sister, a doctor, and has spoken out before about the tragedy of losing her third child 32 weeks into her pregnancy.
'Ben and I did spend some time with our little boy, we named him Willem and we took photos,' she wrote in an article for the Telegraph.
'It wasn't easy but I'm so grateful that even though I never saw him open his eyes or smile, at least I held him and told him how much he was loved.'
During her talk at the festival, Marina also spoke about the impossible standards that social media sets for mothers, and how women should be encouraged to admit to and celebrate imperfection.
'I think this whole strive for perfection is quite suffocating actually for this generation,' she said.
'You have people being able to curate their image really well on social media, it's sort of bragging but it's acceptable because it's on Instagram, which is a bit odd.
'I think an admission of imperfection is really important. To sometimes say I'm not the perfect mother and I don't always cook the perfect food and sometimes my holidays are a nightmare because the kids got ill or whatever it is.
'I think there is a pressure because you have other people's Instagram which is always filtered and carefully selected and in your home the whole time.'