Call the Midwife creator Heidi Thomas: "We are still feminist, we are still furious"

The BBC1 drama's seventh series takes us back to Poplar in East London, where the streets are blanketed with snow and the roads have become sludge. The year is 1963 and London is in the middle of the Big Freeze. Through the blizzard comes the show's first-ever West Indian midwife, Nurse Lucille Anderson (Leonie Elliott), ready to join her new colleagues at Nonnatus House.

Call the Midwife is a series that puts women at the centre of the story – a successful strategy that saw more than six million tune in on Christmas Day to watch the midwives celebrate the festive season. The show has earned multiple National Television Awards and was named the Best Drama of the 21st Century by Radio Times readers.

Speaking at a special screening in London, Thomas is clear about the biggest star of the show: "It is the uterus. And its ability to break hearts, to make lives, to shape destinies. So let's hear it for series seven and the uterus!"

Each episode sees Sister Julienne (Jenny Agutter) and her team of midwives guide the women of Poplar through pregnancy and birth, love and loss, and the early days of motherhood.

These women are dedicated to their jobs and their patients, and they support each other as they face difficult and emotional cases, many of which will bring viewers to tears. The show does not shy away from tricky subjects like stillbirth, poverty, racism, postnatal depression or disability.

So "the uterus" may be the star, but childbirth is only half the story.

Call the Midwife is unequivocally a feminist drama, but it's also a period drama – and that means it must remain true to the realities of the 1960s. That's why, surprisingly, series seven will feature a beauty contest. And Nurse Valerie Dyer (Jennifer Kirby) will be taking part.

"Actually it really works for Valerie, because she's just the kind of person that does muck in. Even though something might seem that maybe it would make her uncomfortable, it doesn't," Kirby says.

Nurse Trixie actress Helen George adds: "The beauty contest thing was quite an anomaly because we were - 'Well we can't have a beauty contest, this is a very strong female show! It doesn't feel right!'

"But historically it was so correct and accurate to do that, but with our modern eyes we were absolutely appalled that we would have to do a beauty contest. But it makes complete sense and it just goes to show the progress that we have made now, looking back on feminism in the sixties."