Q&A: I have an incompetent cervix and had the cerclage done at 15 weeks, then cut at 35 weeks.

Your question raises several points. If you went to full term after cutting the cerclage at 35 weeks, did you really have an incompetent cervix? Did you really need a cerclage? And do you need one with your next baby?

Yes, you probably do have an incompetent cervix and probably did need a cerclage. You're confused as to why, with your incompetent cervix, you didn't just pop the baby out when the cerclage was snipped. Based on such an outcome, I can see how you may wonder about whether you really need a cerclage for the next pregnancy.

Don't be fooled.

In diagnosing an incompetent cervix, it's better to overreact than under react, because the cerclage itself carries low risk. Conversely, if you need one but don't have it done, you can lose the baby. So if your doctor had enough reason to label you as having an incompetent cervix for one pregnancy, it would be prudent to assume you will have it for all of your pregnancies, complete with the need for cerclage. An incompetent cervix won't spontaneously "heal" and become competent.

So why were you able to go a month beyond the cutting of the cerclage? Why didn't your baby just fall out when the trap door was sprung by snipping the cerclage?

First you must consider what type of pregnancy loss occurs with an incompetent cervix. It usually occurs late in the second trimester, or early in the third (between 20 and 24 weeks), when the baby is no larger than a pound or so. A 36 week baby, on the other hand, can be anywhere from four and a half to six and a half pounds. What happens is that the incompetent cervix cannot hold in a small baby that falls against it with gravity, causing a pre-term delivery. Hence the need for a cerclage. But a baby that is four to six times bigger will be so big that his or her head cannot fall so easily into the pelvis, against the cervix, and act as a dilating wedge. In fact, if the baby gets big enough, which is the whole idea of the cerclage, its sheer size will give it its best protection. When your cerclage was cut at 36 weeks, your baby was big enough so that engagement into the pelvis would only be triggered by the forces caused by early labor.

Of course, should you have a very large pelvis, then the bigger your pelvis, the later in gestation this size-dependent protection will occur.

In other words, a successful outcome offers no protection for subsequent pregnancies. Your full-term delivery changes nothing. I'd follow your doctor's advice on this, because you just can't knock success, and that is what your doctor had with your last pregnancy.