Jessica Raine as Jenny Lee in the moving, intimate, funny and true-to-life series “ Call the Midwife.” (Laurence Cendrowicz)

Nostalgia, early feminism and optimism make good medicine in PBS’s latest British import, “Call the Midwife.”

A sentimental, sweet and frank BBC series about a young, idealistic nurse serving the poor in post-war London, the show looks for and finds meaning in life’s most difficult moments.

“Call the Midwife,” set in the late 1950s, takes a page from the groundbreaking AMC series “Mad Men” and begins in an era blissfully unaware of the change bearing down on it.

The medical nuns of Nonnatus House in London’s impoverished East End have long ministered to the physical needs of the poor. But the guard is changing. A brigade of fresh-faced, modern, decidedly secular young nurses gradually replaces the religious charity workers.

One thing seems eternal — people continue to love and have babies. As one sister puts it, “It’s the way it always has been and the way it always will be until they invent some magic potion to stop it.”

The upheaval of the sexual revolution is, as yet, unimagined. With most of East End’s births happening at home, the nurses and nuns focus primarily on easing life into the world.

Jenny Lee, a young nurse from a sheltered background, arrives at Nonnatus House eager to serve but naive. She moves in, acquiring not only patients but a sisterhood of mixed characters. Earnest Cynthia (Bryony Hannah) plays straight woman to irreverent blond bombshell Trixie (Helen George). They are joined by Chummy (comedian Miranda Hart), a clumsy blue-blood bucking her domineering mother’s society expectations.

These girls are as interested in local nightclub after hours as they are with their job on the clock. They are at the forefront of feminism — women who rejected or postponed marriage for a meaningful career.

For Jenny Lee, played with serious determination by Jessica Raine, the desire to work dovetails nicely with hiding from a hopeless love affair.

Sister Bernadette (Laura Main), the youngest nun, enjoys the tittering of the secular girls. Prickly Sister Evangelina (Pam Ferris) and kind, efficient Sister Julienne (Jenny Agutter) round out the house.

Whimsy and wisdom flow from elderly Sister Monica Joan (Judy Parfitt), a woman whose cheerful eccentricity may or may not be the onset of dementia.

The characters run a bit too much to British central casting: the earnest one, the sexy one, the clumsy one, and the cranky nun with a heart of gold, not to mention the aggressively eccentric old nun. They are comfortable, if not particularly innovative characters, well-drawn but not challenging.

Their clients tend to be more, shall we say, unique?

One Spanish war bride has produced 24 little Brits, all without knowing a word of English. Another — a pregnant, prostituted teen — imagines herself in love with her abuser. A kindly old veteran lives happily in squalor and filth, which is disgusting to Jenny’s nursing sensibilities.

Even these quirky characters are not particularly complex. Every person in East End, from the fishmonger at the pier to the priest running the halfway house, has pure motives. It’s a community composed entirely of Downton Abbey’s Mr. Bates. There are no villains in the midwives’ world, merely people finding love and happiness despite their poverty. Cynical viewers may find the show too sentimental to bear.

Those who like happy endings mixed with medical drama will love it.

Unlike TV in the time period in which it is set, the series does not shy away from explicit portrayals of pregnancy. The main attraction is birth in all its desperate, bloody glory — from blocked milk ducts to enemas to afterbirth.

The camera matter-of-factly enters the birthing room with the nurses. It does not mute the agonized cries of labor or the frantic pushing that marks the final moments before birth. Deft camera work catches little heads emerging, although the parts from which they come are obscured by a convenient leg or handy blanket.

With the mothers, the viewer endures the pain of labor to reach the euphoria of the sound of a baby’s first cry, the sweetness of a newborn’s head on his mother’s still-heaving breast, the relieved joy of a gobsmacked new father.

Unabashed portrayal of the facts of life and adoration of career women adds up to a soft feminism. No one burns her brassiere, but neither does she submit entirely to a patriarchal society. There is nothing strident about this portrayal of women, but it is unapologetic nonetheless. Women continue doing what they have always done — bring life into the world and care for each other.

Centering as it does on reproduction before the sexual revolution, one might expect the show to take sides in the reproduction wars of recent memory, but it does not in the first six episodes provided for review. Abortion is only briefly mentioned; it’s a topic unexplored. Birth control is unimagined and not particularly desired.

Instead of picking battles, “Call the Midwife” honors the courage of mothers bringing children into an uncertain world, as well as the women dedicated to serving them, all in a time gone by.

Rebecca Cusey is entertainment editor and lead critic at Patheos.

Call the Midwife

Based on the memoirs of Jennifer Worth, a London nurse from the 1950s to the 1970s, the show airs on PBS starting Sunday, Sept. 30 at 8 p.m.