Ultrasounds in Women of Size, part 1

Recently, a commenter asked about ultrasounds in women of size, and I'd like to briefly address that here and then refer folks to the very in-depth article I have on the topic over at my regular website. 

Remember, if you don't see your question answered here on this blog, I do have my http://www.plus-size-pregnancy.org/ website that covers a lot of these topics in far more detail, complete with research references. The two sites are meant to be complementary.  If you don't see an answer here, be sure to check out my main website.

[Normally, I'd answer the commenter's question on the page of the original post, but I can't easily figure out which post that is.  If there is some way on Blogger to know which post a comment goes to once approved, please let me know!  Otherwise I end up having to go back through zillions of posts trying to figure it out.  I make a best-guess stab at it and if I can't find it easily, I give up.]

Ultrasounds in Women of Size - General Information

Ultrasounds in women of size can be more difficult to do than in women of average size, but most of the time they are quite doable and most women of size get an adequate ultrasound result. 

It is true that extra adipose tissue on the abdomen CAN make it harder to get a completely accurate ultrasound "picture" so the task is definitely harder in fat women. Because of this, it is possible to sometimes "miss" a problem in women of size that might be caught in a smaller woman.  In particular, research shows that it is particularly difficult to get complete evaluations of the fetal heart in women of size. To a lesser degree, there can be difficulties with visualizing the fetal spine, the cranio-facial system, the fetal kidneys/urinary system, and the mother's ovaries.

Therefore, it's not uncommon for the ultrasound report to note the mother's obesity and whether there were any problems completely visualizing anything.  Don't take such comments personally; it's simply CYA for the ultrasonographer, in case something turns up later that was not noted in the ultrasound report.

Simply noting adiposity on a report is not fat-phobia; it's for liability purposes, not to make you feel badly.  However, berating you about your fatness, telling you that they'll never get a decent picture because you are so fat, or treating you roughly with the justification that it's "harder" to get good images because of your fatness is fat-phobic treatment. 

It's not just what they say, but how they say it, the intent behind saying it, and how they treat you.  Most women of size have unremarkable ultrasound experiences, but now and then some do experience fat-phobic treatment and that is never acceptable.

Transvaginal vs. Transabdominal Ultrasounds

There are two methods typically used for ultrasound in pregnancy:

• Transvaginal ultrasound
• Transabdominal ultrasound

In the beginning of pregnancy, fetal structures are particularly difficult to see via abdominal ultrasound in most women, regardless of size, so most women have transvaginal procedures if they have ultrasounds in their first trimester. 

To do a transvaginal ultrasound, doctors take a long cylindrical ultrasound transducer, cover it with a condom, and put it inside the woman's vagina where they can move it around as needed. This gets the ultrasound closer to the fetus, there is less intervening tissue to impede transmission, and it therefore improves the quality of the images.

Transvaginal ultrasounds are common in the first trimester of pregnancy in women of all sizes.  They are usually done in order to date the pregnancy more accurately and/or to tell if the pregnancy is viable.

In the second trimester, doctors usually switch to transabominal ultrasounds in most patients, which are commonly used to look for any problems with fetal structure (birth defects) and to check placental placement.

However, because it is more difficult to visualize the fetus adequately in women of size, doctors may still need to use transvaginal ultrasounds in women of size early in the second trimester (especially women with a lot of abdominal adiposity) in order to get a clearer picture.  By the end of the second trimester, however, doctors are usually able to get adequate images via transabdominal ultrasounds, even in women of very large size.

These are the main differences between ultrasound in women of average size and women of increased size. However, most of the time, reasonably adequate images are obtained and the procedure is very similar, regardless of size.

Possible Problems To Be Aware Of

Although ultrasounds usually go just fine with women of size, there are some possible problems to be aware of.  The first we already discussed; doctors may need to use transvaginal ultrasounds longer in women of size, and the quality of images can be decreased, regardless of the method.

Another problem women of size sometimes encounter is that doctors and ultrasound technicians may press extra hard on women of size to try and compensate for less-clear images. (This has happened to me...ouch!)

Sometimes pressing firmly does help get a better image, but pressing extremely hard can also cause more problems than it solves by distorting the image that they do get.  There have been women of size who have been misdiagnosed with birth defects due to the ultrasound tech pressing too hard.

One woman wrote to me about her experience with this; the ultrasound tech pressed extremely hard, despite her protestations, and they got a devastating diagnosis.

Jessica's Story (paraphrased): I had an ultrasound at 18 weeks. I was told my weight made it impossible to scan the baby, and they saw encephaly [Kmom note: Hydrocephaly?] on the scan. They told me he was going to have a grossly misshapen head and that I'd need a c-section. They sent me to a high-risk OB. He saw the scan and said, "Wait a minute, you're pushing too hard! Do a vaginal!" They did the vaginal and there was our rascal, safe and sound, the right size, and no deformity. I was sore for a week after the abdominal scan, the transducer hurt so bad.

What happens when they push too hard is they distort and add artifact to what they can't see, and the baby looks deformed to their measurements.

If you are told that your baby has deformities or other problems based on an ultrasound scan and they seemed to be pushing pretty hard, ask for the scan to be repeated with a transvaginal scan or by a perinatologist (who usually has the most advanced equipment). Although it is uncommon for images to be distorted from too-strong pressure, it has happened, and should be ruled out as a cause before making a final diagnosis.

Although more firm pressure may be needed on women of size, you should NOT have to endure pain during an ultrasound. If you experience this problem, let the tech know that he/she is hurting you. Let them know that you realize that doing an ultrasound on a heavy person can be more difficult, but suggest that they try more gently at first and only increase pressure if needed. Remind them that if the results they get are suboptimal, there is always the option of a transvaginal ultrasound instead. If they don't listen, then end the session and ask for another session at another time with someone who will listen to and respect your concerns and discomfort.

Improving Image Quality in Women of Size

If your doctor or ultrasound tech is having difficulty getting an adequate image on you, there are several ways to improve image quality in a woman of size. 

For example, often just coming back for another ultrasound in a few weeks is enough to "see" everything more clearly. The baby is older, the uterus has lifted up out of the pelvis a bit more, and the baby may be in a better position the second time. These factors can be very important. 

Research shows that just waiting a few weeks is usually enough to get adequate ultrasounds in most women of size.  Probably the best alternative is simply to wait until 18-20 weeks to do an ultrasound at all in women of size, since after that point, most scans are able to get adequate results. 

Requesting that a follow-up ultrasound be done on a more powerful machine in a center that specializes in prenatal ultrasound may also improve results as well. Not all ultrasound machines are of equal quality; the ones in a doctor's office tend to be the least effective.  Furthermore, it can be very helpful to see someone who specializes in prenatal ultrasound for a living, because they often have the best skills in how to elicit clearer images. 

There are also several other refinements that can be done if the technician has difficulty resolving the images adequately. First, if you have a large "apron" (saggy belly), pull it up and hold it back so the transducer can go underneath/below it. This reduces the amount of adipose tissue the transducer has to go through and can therefore improve the image.  Don't be embarrassed if you are asked to do this; your body is simply your body, lots of people of all sizes have droops and sags in various bits, and it's not that uncommon in diagnostic tests to have to pull and push things this way and that a bit. Be matter-of-fact about it and just do it. It really can help.

Turning on your side and putting the transducer on the side may also help clarify the images, especially if the baby's position is less than optimal, or if there are multiple babies inside.

Another technique they can use to clarify images later in pregnancy is to put a vaginal transducer inside your belly button. Some research has reported success with this, especially with visualizing the fetal heart.

Rosenberg (1995) reported on their experience using transvaginal probes in the belly buttons of obese women to help improve ultrasound resolution. 19 of the 25 cases involved incomplete imaging of the fetal heart. Techs filled the women's belly buttons with ultrasound transmission gel, and then a transvaginal probe was inserted into the belly button. This improved image resolution and resulted in satisfactory heart images in 18 of the 19 women with incomplete fetal cardiac reports. All told, 24 of the 25 heavy women (96%) were able to have a 'complete fetal survey' using this technique.

Remember also that not all problems with ultrasound imaging result from fatness.  If the baby is in a poor position or if the placenta is anterior (in the front), this can decrease the accuracy and clarity of the images.  Technician skill and the power of the ultrasound machine can also impact results.

So although it's true that ultrasound accuracy is definitely lessened in women of size as a group, it's difficult to know whether the problem in any particular scan is due to adiposity or any one of many other factors.  Don't take it as a personal indictment if there is a problem with your scan; be aware of the possible problems, know the possible fixes, and consider trying again in a few weeks if you feel it's really important to have a complete scan. 

Coming Soon: Do Women of Size NEED Extra Ultrasound Scans? What are the pros and cons of having ultrasounds?