This may be a long one but I thought I'd give as much detail as possible, hope it helps!
Based on no history, the Sonographer at my 20 week scan thankfully spotted my cervix was thinning (16mm) and funnelling too. Now 28 weeks and going strong!
I saw an obstetrician who confirmed this on the same day and strongly advised the stitch be put in asap. It would have been on the same day but they couldn't fit me in, so I was put on super strict bedrest until the stitch was put in 3 days later (only getting up to use the toilet or shower - luckily DH was working from home!) They also gave the 400mg Cyclogest to take from the day I had my scan and I am still taking it. I had to take the Cyclogest vaginally until the stitch, then rectally after that to minimise risk of infection.
From the night before the procedure, 2am onwards, I was told to fast, meaning no liquids or food. I had to get to the hospital for 10am and was scheduled to go for the procedure around 11am, but due to a few emergency C-Sections this got pushed to 5pm. I was starvinggggg! I did ask the midwives a couple of times if I am allowed a drink or small snack but got told I can't. The anaesthetist was a little annoyed when he came to see me before the procedure as the midwives should have popped an IV on me for the day at the very least.
So the anaesthetist talked me through his side of things, how I would be having a spinal block and that the most common side effect is a bad headache the next day. He also emphasised the backaches that are commonly mentioned are usually due to having to stay still for so long not due to the spinal.
Once I'd got my gown etc, I was taken to the theatre. Spinal was fine, I did feel a little prick but really was nothing to be scared of (I was expecting it to be quite painful!) He did have to fiddle around a little as I did feel multiple little jabs but it really wasn't a big deal. Not long after I had pins and needles/numbing feeling in my bum then legs. He used a cold spray to check if I was totally numb before anything happened. A midwife was present and even pinched my leg quite hard to show me just how numb I am compared to my arm. I felt her doing it but no pain in my leg.
The rest of the theatre "crew" came in - must have been around 10-ish people all with their own jobs. I didn't feel super exposed and they did pop up a sheet below my chest so I could only really see the anaesthetist, who was monitoring and syringing into my cannula when needed. I did get the shakes which were odd but fine!
Felt a little bit of tugging but barely, and literally no pain at all. Once the procedure was done they showed me a quick ultrasound of baby and I was moved to recovery. The whole thing must have taken 45min - an hour max, the procedure itself around 15-20 mins.
Once I was taken to recovery they just monitored me every 15 mins and all was well. A Catheter was put in during the procedure which I didn't feel at all. It was removed in recovery and just felt a bit odd but again no pain. They wanted me to eat, try to walk about and be able to release at least 150ml from my bladder - this all happened within 3 hours and I could go home (10pm). So although I was there all day, technically from the procedure to being discharged was 5 hours.
I was told to continue with bedrest, cyclogest (rectally), no sex, nothing going into the vagina. I have had 2 follow up checks by obstetrician (every 4 weeks) and the stitch has been holding up so far with cervix being at around 19-20mm.
After my 27 week check up I was told I can just have sofa rest and take it easy, no heavy cleaning/ minimise stairs / only carry light stuff around. The rest of the no sex etc still holds unfortunately!
I would advise drinking loadssss of water - I've been aiming for 3 L per day and found I didn't get any headaches, cramps or constipation during the strict bedrest and it is also good to keep up fluids anyway during pregnancy!
Each experience is completely different and advice will of course be tailored to your individual situation. Hopefully you won't have to do bedrest (it is a hotly debated subject but I followed the consultant's advice and it was an emergency/rescue stitch rather than preventative).