Is something wrong with the uterus or cervix?
Previously I have referred to the fact that an incompetent cervix is a very common cause of second trimester miscarriages (those occurring sometime between the 13th to the 24th week). Now I want to focus on the known reasons why incompetent cervix occurs and what can be done about it.
In chapter 3, I discussed the female anatomy and process of development of the embryo, pointing out how very early in the life of the embryo the sexual organs are created. It is now well known that congenital abnormalities (meaning those abnormalities you are born with) of the uterus can cause second trimester miscarriages. For this reason, one of the major points of investigation for any doctor will be your medical history relating to the uterus.
The fallopian tubes, uterus, and the upper portion of the vagina are all formed within the first 5 to 6 weeks following conception (again I am using a more accurate method of dating; form two structures known as mullerian or wolffian ducts. The mullerian ducts form the reproductive organs, and the wolffian ducts from the kidneys and urinary tract. Both are of vital importance in the developing female fetus. Between the 6th and 7th weeks following conception, these ducts begin a process of change, during which problems might occur.
In the 9th week, the two mullerian ducts cross above the wolffrian tract, where they fuse in the middle of the body to form a single cavity that will become the uterus and vagina.(in the male embryo, the same cavity will have degenerated by the 10th week.) the vagina dose not open as a canal, however, until the 20th to the 22nd week. At any stage during this normal course of fusion something can go wrong.
Heredity may play a part in the abnormalities, or drugs such as DES taken by your mother could also be responsible. DES not only damaged the vagina in many female fetuses, but it led to a special form of uterus abnormality known as the T-shaped uterus.
The most common diagnosis, in about 50 percent of cases, is of a bicornuate, or a septate, uterus, where a band extends down the middle of the uterus toward the cervix. With a didelphic uterus, there are two separate cervixes too.
Some of the more common abnormalities may have been caused by one or both of the mullerian ducts failing to develop, leading to an absence of one half of the uterus。Or the ducts ,ay have failed to fuse, leaving uttering structures without proper cavities.
Such abnormalities of uterus are more common than doctors used to think. Studies performed on women who are evaluated for infertility show congenital abnormalities of the uterus as frequently as frequently as 1 to 10 percent of this population. However, in a recently reported study of women sterilized through the cervix, the incidence was 1.9 percent. This later figeure is probably more typical for the general population, in that this was a group of women not experiencing trouble conceiving. Nevertheless, a statistic of nearly 2 percent is still a very high one.

How do we discover these anomalies?
If your doctor feels that your history indicates structural defects—typically that would include unexplained recurrent miscarriages in the second trimester—the procedure known as hysterogram (HSG) will usually be performed. A radiopaque dye is injected through the cervix to fill the cervix canal, uterus, and tubes.

This X-ray procedure allows the radiologist to see clearly the dye passing as it is injected, giving the shapes of the relevant parts in the cervix, uterine cavity, and tubes. Unfortunately, it can be quite uncomfortable, leading to cramping that may be moderate or, in some cases, severe. You would be advised to request an experienced and sympathetic radiologist. Though it is not usually performed under a general anesthetic, a local anesthetic can be given in the cervix. You may also be given antibiotics, before and after the procedure, to avoid any risk of infection from the dye being injected. You should try and arrange the date of the procedure for just after a period to make sure your not pregnant during the exposure to X rays.

Certain other terms you may hear in course of such investigations will include laparoscopy, which is the method of inspecting the uterus and tubes by looking through an instrument (laparoscopy)   inserted through umbilicus (belly button). Prior to insertion of the laparoscopy, your stomach is filled with 3 liters of carbon dioxide gas. The laparoscopy is used for direct visual examination to support a diagnosis. You will be brought into the hospital for a day, as the procedure is performed under a general anesthetic.

At laparoscopy, a double uterus or a partially split uterus may be seen. The doctor can also see whether your tubes are bound by adhesions, or whether there is endometriosis in the pelvis. Dye is injected to see if it spills readily through the tubes. Your appendix will also be checked to see whether it is healthy. Following the procedure, you will have a few stitches in the umbilicus and possibly a stitch in your pubic hair region where a probe may have been placed. The stitches will not need to be removed because they dissolve on their own.

Hysteroscopy is a relatively new technique that also provides visual examination, but this time of the inside of your uterus. The entry is made from below, through the vagina and cervix, using a special fiber-optic hysteroscope. For this procedure, the cervix is dilated, using a cervical block or general anesthetic, and the uterus is inspected along all its walls to look for abnormalities such as congenital bands or achesions. These can be treated at the same time, through the hysteroscope, making it a very helpful test.

Now your doctor can confirm his diagnosis and define any abnormalities. These types of investigations once would only have been performed on woman with infertility problems. But now, more and more, they are being used on women with a history of miscarriage. This procedure which corrects uterine deformities from inside the uterus, performed with the help of the hysteroscope, may avoid the need fro abdominal surgery to correct the shape of the uterus (known as metroplasty). As with any form of abdominal surgery this would mean not only the involvement of general anesthetic and a length recovery time, but also the uterus being opened uo, which may lead problems in a future pregnancy. 

Following corrective surgery on the uterus, the success rate for a healthy birth is about 80 percent. But, as ever, the advantages of surgical technique have to be weighed against possible risks. Surgery may cause scarring of the uterus, which could affect your fertility. Where surgery is not required to correct a congenital abnormality of the uterus, treatment may varying from nothing, to placing a suture in the cervix when you next become pregnant.

Ultrasound is also being used as yet another technique to diagnosis abnormal uterine structures. Ultrasound carries the advantage of being safe and painless. But it does require an expert sonographer to interpret what is being seen on the screen. Until more expertise is gained, ultrasound is mainly used as a screening procedure prior to something like a hysterogram.

A simple test often done in the doctor’s office to see if your cervix is incompetent (weak) and in need of a stitch is to pass metal dilators (Hegar size 6) gently into your cervix. If they pass easily, that will mean you have an incompetent cervix.