Information about Cerclages.
The cerclages fall into 3 types - McDonald - a pursestring stitch around the cervix to cinch it together, Shirodkar - a pursestring stitch around the cervix underneath the skin of the cervix to help cinch it together, and an abdominal cerclage - a stitch around the lower part of the uterus through an abdominal incision to cinch the lower part of the uterus and upper cervix together. They all have risks and benefits.
Once you have an IC, we pretty much always suggest putting a cerclage in before you start dilating, usually 12-14 weeks. That time is picked so that most miscarriages will have happened and we can look with the US to see that there aren't obvious abnormalities. Not that we can see them all then, but some you can.
Once that has been done, the cerclage is placed. The difference between the cerclages is small - mostly depending on which one the doc is most used to. The Shirodkar and the McDonald are both "pursestring" sutures that go around the cervix to try to hold it closed, just like the around a drawstring purse or the string around the inside of some stretchy pj's to tighten the waistband. We put the string in and tie it tight to hold the cervix together. Just like the string in the purse, if you put enough pressure on it, it will rip through and it you put something elastic (like a water balloon for example) inside, you can ooze it out through even a small hole in the cervix (which there always is even when you are trying to close it up tightly). So those are the risks to watch for along with infection. Nevertheless, they usually work well.
To make a long story longer, the difference between them is (finally) that a McDonald is just like a pursestring - it goes in & out of the skin covering the cervix until it is all the way around. Then it is pulled tight, gathering the cervix together, and tied tightly. You can see the string in several places as it comes out of and goes back into the cervical skin all around the cervix. The Shirodkar does the same thing but underneath the skin of the cervix. A little incision is made, a special needle used to tunnel under the skin from the incision at 12 o'clock on the cervix to 6 o'clock. Then the string is placed back into the 6 o'clock hole it just came out of and tunneled under the skin back up the other side of the cervix back to 12 o'clock. Finally, the string is tied tightly and the knots and ends covered over with the skin which is sewn closed. That buries the string altogether, possibly reducing the risk of infection (not proven) and some feel it is stronger. Both work well, most of us use McDonalds because it is easier. The Shirodkar could be permanent (then you would need a C/S) or taken out near term. The McDonald is taken out. The only other practical cerclage is a permanent one inside the abdomen when there is too little cervix to sew up the regular way.
Fred Coleman, MD
Dr. Coleman has been practicing obstetrics for 24 years, has a subspecialty in maternal-fetal medicine (high risk pregnancies), and currently works at the hospital at the University of Oklahoma.