''Here we bloody go again!'' ''Breathe through it!''

With a push and a pop, season three of Call the Midwife arrives, fresh with the promise of a new era as the midwives and nuns from Nonnatus House move to new digs and busy themselves with getting the telephone to work.

That's just the scaffolding, of course, for bigger change is afoot - it's 1959 and the swinging '60s are around the corner, with all the social change they will bring.

And while it would be easy to focus on the small stuff - how on earth does nurse Jenny Lee (Jessica Raine) manage to make house calls on a bike, sit up all night helping a woman give birth and keep her hair in the most perfectly pinned curly up-do? - I'm hailing Call the Midwife for what it really is: a feminist tract disguised in a red cardigan and sturdy brogues.

While it treads a fine line between rose-coloured nostalgia and being annoyingly twee (especially Miranda Hart's Chummy and her grating bally-bally-botheration-style speech patterns) and its vision of London's gritty East End is suspiciously glossy, Call the Midwife is about women taking control of their lives.

It's women leading women through childbirth, women taking control of their health and women finding fulfilment through family and work. It's nuns and midwives living and working together in an era when many women had the decisions about their lives made for them by men - husbands, fathers, doctors.

In Call the Midwife, however, the men are mere distractions as the women forge an independent path (aided by an enormous amount of cake and buckets of tea). Tonight, it's that very question of independence - from family - that comes to the fore as Chummy struggles with the ''calling of marriage''. Sure, looking after baby Fred and placing decorative radishes in her husband's lunchbox is oddly satisfying, but it can only get a career-minded lady so far.

So what does one do when cushion-making isn't enough to pass the time, especially when your former colleagues are diagnosing cystic fibrosis from the taste of salt on a baby's brow?

For Chummy, the answer is to create her own brand of chaos by turning the opening of the baby clinic at the new community hall into a royal to-do (enter Princess Margaret, who is able to attend with less than a week's notice …).

She's just trying to keep busy, of course, for what she really craves is her work but, as for many women, giving voice to these feelings is harder than it looks, even when it's clear to all what the problem is.