The television drama Call the Midwife, with its Sunday night BBC1 slot and 10 million viewers, has become what they call A Surprise Hit. I am not sure why. Not why it is a hit as it's a brilliant bit of telly, but why it should be a surprise. I can see why a programme called "Call the Accountant" might not set the ratings alight, unless it was about getting raided in the Seventies for siphoning pop stars' earnings into offshore bank accounts and Quaaludes. "Call the Postal Worker" doesn't quite have that ring of emergency to it. And "Call the Information Resources Centre Strategy Consultant" is too long to trend on Twitter. But midwives, in this case, bicycling through the East End fog in the Fifties, are at the centre of the maddest action possible. People sprouting out of other people from between their legs, having grown suspended in liquid, now entering the world to get their first taste of the addictive drug that is air. Humans at both their smallest and their most impactful. Half-naked women, so tired, so strong. It's not exactly dull.

And yet the show's writer, Heidi Thomas, has just revealed in an interview that "we were told men would not watch and young women would not watch and pregnant women would not watch, which would have left only a very small audience". Turns out nobody can resist things like the home that contains 24 children and a glorious Spanish wife whose cockney husband brought her home after fighting in the Civil War – and they've never lost a baby until this one, who comes out premature and blue and dead, placed quietly on the side to be disposed of. Until he squawks.

I was recently in labour at London's wonderful Homerton Hospital for so long that I got through nine midwives. Yes, nine. Even through my bleary, drugged haze, I did wonder if the national midwife shortage was anything to do with the fact that all of them had been called to my bedside. And as one of them said to me – or did I read it somewhere, or did somebody else tell me that they read it somewhere, man, those drugs were good – being a midwife means being present at the most amazing day in somebody else's life. Every single time you go to work. The most amazing day that can also bring ecstasy or tragedy or pain. All three. That compelling TV drama could come from this is hardly a shock.

But is it the Fifties aspect that really pulls us in? Is it part of our Sunday night nostalgia, our wave of period TV dramas like Downton Abbey, all harking back to a time when if somebody needed to tell you something important they couldn't just yank their phone out of their pocket: they had to run across dusky streets and yonder meadows to bang on your door and tell you? In the case of Call the Midwife, it shows us why we have a welfare state. It shows us the conditions in which people lived in the first half of the 20th century, just a few miles from the corridors of power and the Crown Jewels.

So maybe it isn't nostalgia at all. Maybe we like these programmes because they remind us we are at our most dignified when we attend to each other. In Call the Midwife (based on the true story of Jennifer Worth), the midwives attend to people who might otherwise fall under the radar. Teenage prostitutes, dirty children, the poor. The happy, sometimes, too. People who might not be expected to amount to much, and yet, as we see, and as our current welfare-hating government would do well to observe, they do.