I had b/g twins at 27 weeks + 6 days.
I know when you read that (if you haven't got any experience of premature babies) that it is really alarming. I remember being about 20 weeks pregnant with the twins and reading the story of a twin mum to be who had been told she had to have a section at 32 weeks (the earliest I'd ever known babies to be born) and was flabbergasted. When I was told at 27+4 that they'd try to stop my (spontaneous) labour (which I thought was just back ache), they could only stop it for a while and I would deliver within days, I was completely and utterly devastated and thought they would never survive. It had been a completely smooth pregnancy up until that point.
They were 2lb 6oz each when they were born (naturally) and were whisked off pretty quickly to Neonatal Intensive Care. Don't get me wrong, it was horrible but the progress and developments that have been made in recent years mean that they weren't even classed as "very early" from a medical point of view. After about 48 hours, the consultant said that they were in hospital just to learn how to feed and get bigger.
I'm always in 2 minds about posting something like this - just wanted to reassure you really that if you do end up delivering early, its hard of course it is, its a bit of an emotional roller coaster, one always seems to do better than the other, if they're ever split up (i.e. not next to each other in their incubators / cots) you feel like you want to split yourself in half and leaving them in hospital when you've been discharged is heartbreaking. BUT (and its a big but) I genuinely feel like neonatal drs and nurses are the most incredible, understanding, professional people you'll ever come across and you'll get through it.
My twins were in NICU / SCBU for 8 weeks and 5 days - so came home at the equivalent of 36+4. They had regular check ups and were completely discharged when they were 2yrs old. 6 years later, my DS is on every sports team going (and bright too) and my DD is at the top of her class with a reading age of 11. No signs whatsover of their prematurity.
Good luck. Hope I haven't worried you, wanted to give you a positive story.
Mandy