Nine Week Gestation with Retroverted Uterus – Well, this is confusing?!
When performing a transvaginal ultrasound in the first trimester and the uterus is retroverted, things can get a little confusing. Unless you have a good foundation of probe orientation and scan planes, you may feel as though you are scanning backwards or even upside down. It is important to establish uterine position during your initial sagittal sweep through the pelvis, as you are also evaluating for the 5 A’s.
Before we begin the case study. Let’s review image orientation for transvaginal scanning of the pelvis. Below is an image of an anteverted uterus.
The image on the right is a normal ultrasound image. The image on the left is twisted as if you were scanning transabdominally. This helps to show you the difference between the transvaginal approach and the transabdominal one.
Anteverted Uterus
Retroverted Uterus
The image above is a transvaginal image of a retroverted uterus.
The difference is that the uterus itself is in a different position, but the scan plane doesn’t change. In the sagittal plane, with the probe notch up, notice how the fundus points posteriorly or toward the patient’s spine with a retroverted uterus.
Don’t let the uterine position trip you up and/or confuse you.
In the following case study, you will see a 9-week gestation with a retroverted uterus and how the protocol really is no different.
Case Study
Patient presented as a 35-year-old G3P1 with a positive pregnancy test. LMP is noted to be March 15. The patient has had 1 prior SAB.
Show Intrauterine Pregnancy
Transvaginal ultrasound was performed on May 23. While performing the initial sagittal sweep through the pelvis and evaluating for the 5 A’s, we can see that there is a retroverted uterus and a single intrauterine gestational sac. Notice in the still images below that the fundus of the uterus points posteriorly or toward the patient’s spine as we discussed earlier.
Establish Viability
Since we established an intrauterine pregnancy, we can zoom up and evaluate the fetal pole. Using m-mode only, we can measure the fetal heart rate which was normal at 175bpm.
Crown Rump Length Measurements
After that, we measure the CRL three times to get a good average size of the fetal pole.
A normal yolk sac is also seen as pictured below:
Evaluate Adnexa
During the first trimester scan, each adnexa and ovaries should be evaluated. Left and right orientation are still the same with a retroverted uterus. Both ovaries were normal. In the left ovary, a small corpus luteal cyst is seen. This is a normal finding in the first trimester.
Incidentally, there was a small amount of free fluid noted in the cul-de-sac, which is normal and physiologic. Where do you think the posterior cul-de-sac is with a retroverted uterus?
The posterior CDS is found by angling the probe posteriorly toward the patient’s spine and beyond the fundus of the uterus when retroverted – in the same place you would find it with an anteverted uterus (just happens to be beyond the fundus and not the cervix because of uterine position).
A small sub-chorionic hematoma or hemorrhage (SCH) measuring approximately 2.8cm is also seen as pictured below:
Just for fun, we were able to obtain a super cute 3D image of the baby for the parent’s and they were very happy!
Report Page
Finally, we come to our report page. We can see that the fetal pole measured on track with the patient’s LMP of March 15. There is only a 2-day difference, so using the ACOG guidelines for dating a pregnancy, we will not change the due date based on this ultrasound.
Aside from the small SCH, this is a normal first trimester scan. Precautions were given to the patient regarding the SCH, but no follow up indicated at this time.