3D Ultrasound Enhances Diagnosis
For some women, infertility is caused or exacerbated by having a uterus with congenital abnormalities that cause it to be misshapened. These uterine anomalies can lead to greater difficulty with embryo implantation and/or cause higher rates of miscarriage.
Until recently, a physician’s capacity to properly diagnose this problem has been limited to a hysterosalpingogram (x-ray with dye); a MRI (magnetic resonance image); a laparoscopy (surgery which limits the evaluation to the outer contour of the uterus); or a standard 2D ultrasound. The emerging technology of 3D ultrasound is starting to provide a highly improved, noninvasive, more cost effective option. Fortunately in the Bay Area, women can obtain a 3D ultrasound at the CPMC OB/GYN Ultrasound Suite which is directed by Dr. Lourdes Scheerer and two other physicians, Drs. Claire Serrato and Shelly Zaglin.
An ultrasound uses high-frequency sound waves (between 3.5 to 7.0 megahertz) sent through the body via a transducer or a scanner that is placed either on the lower abdomen or inside the vagina. The ultrasound beams scan specific areas of interest within the abdominal cavity and are reflected back onto the transducer to produce an “echo” image of the internal organs. This process had been shown to be both safe and effective.
There are several reasons why a physician would want a 3D image of the uterus, explains Dr. Scheerer. By using a 2D ultrasound one can assess the shape of the uterine cavity, but cannot assess as clearly the positioning relative to other pelvic organs (ovaries) nor the contour of the uterus itself. This information is important in assessing a possible abnormality of the uterus, and on deciding appropriate intervention.
There are some congenital anomalies of the uterus that can impact an embryo’s ability to implant and develop within the cavity. If a woman has an abnormally formed uterus, this can cause a higher incidence of miscarriage or be an obstacle to carrying a pregnancy to full term. In women experiencing unexplained repetitive miscarriages, it is important to rule out the possibility of uterine anomaly as the cause. Women with uterine anomalies can also experience higher rates of preterm labor, bleeding during pregnancy, diminished fetal growth, and fetal malpresentations (such as breech), which lead to a higher rate of Cesarean delivery.
A typical uterus is shaped like a small pear and the cavity within has a hollow triangular form. The uterus develops inside a female fetus by the fusion of two separate halves (Mullerian ducts) into a single organ. The uterus subsequently becomes hollow, creating a normal cavity. Abnormalities in the shape of the uterine body and/or the uterine cavity are called “fusion” defects because they arise from failure in the aforementioned unification and hollowing process. If there is failure of the uterine body to fuse completely, the uterine shape will be abnormal. Because the ovaries are derived from different fetal tissues, the development of the ovaries is not affected by Mullerian defects.
Failure of fusion and hollowing can present as a spectrum of abnormalities from a simple dimpling of the top of the uterus as seen in this arcuate shaped uterus
Arcuate Shaped Uterus
One of the most common abnormalities is a bicornuate uterus.
As shown here, a bicornuate uterus has two uterine horns. Pregnancy within a bicornuate uterus typically occurs within one of the horns and pregnancy outcome is usually as normal as for a fully developed uterus. Surgery is not required for this kind of an abnormality.
The uterine abnormality most commonly associated with miscarriages is a uterine septum
This is an abnormality of the hollowing process where a residual midline septum is present. Normal uterine lining does not grow over a septum, so if the embryo implants in the septum, it will not have an adequate blood supply for growth. The traditional way to correct a septum was performing an abdominal surgery called a “metroplasty”, where the septum was removed, and the uterine walls sewn together. This surgery was not very successful, and nowadays we can remove a septum by hysteroscopy, which provides a much more successful outcome. For a uterine septum, surgery is the correction.
Understanding the type of uterine defect one has is critical, because this will determine if surgical intervention is needed to optimize one’s chances of a successful pregnancy.
A 2D ultrasound can suggest that an abnormality is present, but does not necessarily differentiate among subtle abnormalities. The advantage of 3D ultrasound is that it will better define the specific defect present. Based on this improved image, the best recommendation can be made. 3D ultrasound provides a cost-effective imaging modality, which gives good resolution when differentiating Mullerian anomalies.
Dr. Scheerer reports that 3D ultrasound can also be helpful in differentiating the location of abnormal pregnancies. For example, the improved imaging can be helpful in distinguishing a tubal ectopic pregnancy, versus a corneal pregnancy.
The technology that makes 3D ultrasound so reliable is evolving rapidly, partly due to the sudden popularity among pregnant women who want the better-defined early fetal images for their baby books. While this is currently “in vogue”, it is important to understand that there are no long-term studies looking at the effects of 3D ultrasounds in pregnancies.
While we don’t endorse the use of 3D ultrasound strictly for photo opportunities, we think it is a very valuable tool for finding and evaluating certain uterine abnormalities. This information gives us the opportunity to optimally treat each individual person and maximize the chance for a successful pregnancy.