Catastrophe, Series 2, Channel 4

There’s a baby boom in sitcom. This week two of last year’s best comedies return for second helpings, each with a child in tow. In Detectorists (BBC Two on Thursday) Andy is out in the field panning for gold with a small sweet addition. But first Catastrophe is back – and the title holds good.

For Sharon and Rob (played by series creators Sharon Horgan and Rob Delaney) parenthood is just as much of a disaster zone as the unplanned pregnancy which threw them together in the first series. And the jokes still come at you like rapid machine-gun fire.

In fact, it’s possibly even funnier now. In the first series the odd-couple set-up of an accidental transatlantic love affair was not something most viewers will have experienced. But they will be a lot more familiar with the concept of bringing up babies. It’s an area landmined with potential indignities, already much visited in comedy, but Horgan and Delaney have taken frankness to a lower level all their own.

One of the jokes of this London comedy is that barely anyone in the show is English

The show began with a grave case of coitus interruptus as the boy conceived in the first series walked in on a rare coupling. There followed riffs on the best size for a baby’s penis, mothers obliged to wear nappies, and that orifice where (some) big boys and small like fingers to be thrust. Then, with the second baby due, there was a gloriously foul visit to the delivery suite (“Am I shitting myself now?” “Barely!”). And at the end of it all, a baby shower cake was decorated with an extreme close-up of the newborn plugged onto Sharon’s nipple. (“That's my areoli! You can see my veins!”) Expect, in due course, potty-mouthed jokes about the potty.

It’s dirty, yes, but Catastrophe is written, performed and edited with a clarity that is next to cleanliness. And it’s impossible not to love the protagonists. Horgan’s Sharon is all soft self-pity in inverted commas, while Delaney gives Rob the mind of a cesspit and the soppiness of a dog. (There is an actual dog in the new ménage, but it doesn’t last the episode.) In one beautiful scene they conjured warfare out of the tiniest provocation, telling a genuine truth about the awful things people say to those they love, knowing forgiveness is inevitable.

One of the jokes of this London comedy is that barely anyone in the show is English. Sharon and her family are Irish, Rob is American with a mother from hell played by Carrie Fisher, and their best friends are Scottish, though only Chris (Mark Bonnar) turned up to the baby shower. “Barometrically we combine to create an atmosphere this is somewhat shitty,” he explained coolly. He and Fran tossed to see who’d attend. “I lost,” he shrugged. “No offence.”

None taken in Catastrophe, which tackles the big subjects – sex, birth, marriage and, as of this series, dementia and (dog) death – with maximum irreverence. Please could they get together and try conceiving a third series?

@JasperRees