Raine starred in the leading role as bicycle-riding Jenny in the BBC1 series, set in the 1950s in London's East End, alongside Jenny Agutter, Pam Ferris and Miranda Hart.
She told the Radio Times that her alter-ego, who enrols as a midwife alongside an order of nuns, was "the first rounded character" she had played on TV.
But she added: "I feel very guilty about the way we treated some of the babies on the Midwife set. They were always sleepy and in the scenes where they had just been born we needed them to cry so I had to blow on their face - I felt evil."
A second series of the drama, based on the memoirs of Jennifer Worth, who died last year having sold more than a million copies of her books, begins filming in June.
But Raine, who enjoyed a successful stage career before landing the TV role, said: "I get a bit annoyed when people describe it as cosy. There are really grisly stories and though it's wrapped in this 50s nostalgia it's more than that."
The hit series landed a second series just two episodes into its run after BBC bosses were delighted with record audiences of almost 10 million viewers.
BBC1 controller Danny Cohen commissioned a further run after figures showed it had drawn the biggest audience for the launch of a new drama on the channel.
And here's the very first trailer... sooo obvious it was going to be a massive hit (hindsight being a wonderful thing!)