When season eight looked as if it might be the last - before the agents and the network started talking turkey - there was a rumour that Friends might end with Rachel dying in childbirth. There was, the producers insist, never any truth in it, but its very existence was telling. In the first place, it reflected the pessimism understandably created in America by 9/11. Second, it was a tribute to the credibility and roundedness of the dramatis personae: you don't, as your series' last word, kill off one of your leads unless you're beyond certain that your audience believed she lived and breathed in the first place and shall weep buckets.

But the rumour's third significance was the most worrying. By series eight, the plots in Friends had become more important than its jokes. We - and I confess to having seen all 190 or so episodes - were watching by now to find out if Chandler and Monica would really settle for each other, if Joey's crush on Rachel was ever going to be any more than that, and, above all, if the on-off romance between Rachel and Ross, which had already produced one marriage, two "I do's" from Ross (who named Rachel at the altar while getting spliced to someone else altogether) and now a pregnancy, would finally and permanently flip to the on-position.

Friends remained compulsive viewing, but it was the compulsion of the soap opera. The jokes were increasingly left to Phoebe, and excellent comedian though Lisa Kudrow is, that was unfair. A sitcom in which five out of the six actors are more angsty than funny is not actually a sitcom at all. Rachel's death would have confirmed the programme's drift from comedy to drama.

But, as Dickens would have said, Rachel did not die. She gave birth to Baby Emma - but by the second episode of series nine (shown alongside episode one on Friday 10 January on Channel 4, and the night before on E4) was back in her fantasy apartment, her fantasy figure showing little or no sign of the pregnancy and her love life in as much chaos as ever.

Last year's season had ended with less ingenuity than contrivance, perhaps, with Joey in the maternity room, finding on the floor the ring that the baby's father, Ross, was carrying without much intention of giving it to Rachel. Because he is on his knees, ring in hand, Rachel thinks Joey is proposing and, in postnatal desperation, she accepts. This week's episodes had Ross, with all the delays characteristic of comedies of misunderstandings, being slowly made aware of this confusion and becoming suitably outraged.

The best joke of any Friends came when the six regulars were together in their apartment and someone knocked at the door. The joke was that, with everyone so assembled, no one could imagine who it could be: their universe had so shrunk. What had started as a comedy of independence from family had become, as the cast toppled over the age of 30, a story of co-dependency. The friends were no longer God's apology for family: they were family and they were marrying and breeding together. With Phoebe (the one with the identical twin sister) already having carried her brother's triplets to term, there was a whiff of incest in the air: Chandler and Monica were married; Ross and Rachel were married and divorced and now having an unplanned baby together. Numerical logic urged that the dim-witted Joey and flaky Phoebe would next fall in love and have an idiot child.

This season is continuing to hint that cosiness has turned into claustrophobia. The reason it takes so long for Ross to discover that Rachel has got engaged is that no two members of the cast ever get a chance to be alone together. Phoebe even scolds Ross for wanting to be alone with the mother of his daughter: "You can touch yourself in front of us, but you can't talk to Rachel." And when Chandler and the ovulating Monica retire to a broom cupboard to have procreative sex, they are soon spied upon by Joey and, indeed, by her own father, although this comes across as a lesser breach of taboo. For much of the first episode, Joey tries to avoid looking at Rachel's inflamed nipple as she suckles Emma.

It is a little creepy and, although this series has been hailed in the States as a return to comic form and new writer- producers have been drafted, it is hard to laugh so very hard. The funniest moments have actually come, very unusually, from Chandler's office life. Falling asleep at a meeting, he finds on awaking he has been posted to Tulsa, Oklahoma, by his humourless boss.

Monica: "I don't even want to see the musical Oklahoma!"

Chandler: "Really? "Oh What a Beautiful Morning"? "Surrey With a Fringe on Top"?"

Monica: "Are you trying to tell me we're moving to Oklahoma or you're gay?"

Back in the main plot, meanwhile, Ross and Joey have come to blows and Ross is trying to convince himself that it's "much easier" if Rachel and he remain friends who've happened to have had a baby. I don't know where all this is heading. And I don't suppose the talented team of writers, who have recently learnt that the cast has agreed to a final, final tenth season, know, either. May I suggest a joke?

Andrew Billen is a staff writer on the Times