A cerclage is another name for a stitch put in your cervix. If your cervix looks like it is opening prematurely on ultrasound, your doctor may recommend putting it in.
Of course, if you're pregnant, the thought of any messing around with your cervix is scary. They would never recommend this, though, if it weren't necessary.
Generally, you go to a perinatologist for a cerclage placement. Most obstetricians are not going to put it in.
For the vaginal procedure, you are usually awake, but the doctors will give you an epidural, which is the safest anesthesia when you're pregnant. You'll be lying on the table like you do for a Pap smear, and the doctor will reach up and sew in the stitch as high as possible. The higher, the better to keep more length for your cervix.
Now, if you already lost a baby due to premature dilation, you can have a permanent stitch placed through your abdomen. For this surgery, you are asleep, and the doctor goes in through an incision in your abdomen and sews in a more complicated stitch called a Shrodkar procedure. Your cervix is not completely closed--it is open enough to allow your period to get out and for sperm to get in.
There are some risks to getting the vaginal procedure. One is infection, which is rare. The procedure could cause your amniotic sac to rupture, also rare. And there is some debate about whether or not a cerclage helps prevent pregnancy loss. In one situation, it is absolutely necessary, and that's a trachelectomy.
After a regular cerclage, you usually can't have sex until the baby is born. When you're about two weeks away from delivery, the doctor will snip the stitch out. Amazingly, you don't just drop the baby then and there! You'll probably go into labor naturally around your due date. But if you go into labor a little early, it's fine, too.
After a Shrodkar procedure, you have to have a C-section.
Before you have any problems, find a good perinatologist in your area and go for regular appointments. If your cervix starts to funnel and open, they can catch it and save your pregnancy.