Call the Midwife series 5 preview: It's the season of science, social change and girl power

But now Midwife is back for its fifth series and it's time to get down to business. Series five kicks off this Sunday and it's a strong first episode.

We find out how Trixie has been coping since she admitted her problems with alcohol – she's clad in black lycra as a newly-qualified Keep Fit instructor. Her health kick sparks a storyline about women owning, knowing and taking control of their bodies and their choices.

https://www.youtube.com/watch?v=igUlu_1W-lQ

There's a sense of what's to come, of serious social change and empowerment, with a heathy side order of female friendship and camaraderie.

A photographer arrives to record what's left of the old East End. There's talk of new housing, birth control and men on the moon. The younger generations are pushing away from the restraints of the post-war world. It's a time of possibility and change.

But not all change can be good. Call the Midwife isn't just about cardigans and cups of tea. It's always been a show that isn't afraid to tackle the tough stuff; series four pushed the boundaries of what we expect from the show, and that looks set to continue.

The topic of Thalidomide sent a tremor through Call the Midwife last year, and it's a storyline that is not going away. The disaster came from an unerring trust in science and new advancements – and, however upsetting, we are going to see that error played out on a small scale in the heart of Poplar.

Call the Midwife returns on Sunday at 8pm on BBC1