The sight of Charlize Theron expressing milk and covered in sick really does bring back memories.

Not that I’ve ever seen Charlize like this before – not even as Aileen Wournos – but memories of my own baby caring days did flood back. So tough and dark are these times, you almost consign them to the nappy bin of your memory but here they are again, detailed in a painfully funny montage: nappy changing, breast pumps, howling baby monitors, middle of the night feeds, getting baby down again, the blissful silence of baby stopping crying, dropping your mobile phone on baby’s head, more crying…

Charlize plays Marlo, frazzled by the arrival of her third, Mia, while still coping with the behavioural issues of her second, Jonah, whom a therapist has recommended she brushes every night, like a tiny horse. He’s quirky, say the school, before effectively kicking the kid out.

Marlo’s wealthy brother (Mark Duplass) and his ridiculously pretty wife, offer Marlo (and her put-upon husband, played by everyman schlub Ron Livingston) the services of a “night nanny”. After initial resistance, Marlo accepts and the amazing Tully turns up and turns her life around.

Tully (Mackenzie Davies – she’s going to be a star) is young, beautiful, wise, calm, cool and has a complicated love life. She even makes cup cakes and does the hoovering. Marlo, blessed with her first good night’s sleep in years, is soon dependent on her new super nanny for everything, even for arousing her husband in bed.

This is a typically sharp and funny script from Diabolo Cody (Juno), full of one-liners and observations about modern life and motherhood – annoying do-gooders in the coffee shop warning the pregnant Mum that decaf still has “trace amounts of caffeine”, a dog called Prosecco, a school talent show where one girl’s talent is “Pilates”. And I don’t think I’ve ever seen the mundane grind of baby care depicted on screen like this, so unsparing in its honesty, yet in director Jason Reitman’s hands it remains warm and sweet.

Ultimately, the film is about motherhood but it’s also very much about sisterhood as Marlo and Tully bond, an interplay of generations, a younger and older self. There’s a bit of a lurch in the final scenes, a bit of drama the film didn’t really need. I was happy watching Charlize re-discover her mojo on a night out in Brooklyn, driving along to a Cyndi Lauper mixtape. Girls Just Wanna Have Fun, after all – and babies don’t