As a doula and midwife, I have witnessed countless parents troubled over ultrasound findings that may or may not be accurate. I have seen misdiagnosed abnormalities, wrong gender predictions, both gross over-estimates and under-estimates of weight which can lead mom to fear labor or even be induced in fear of baby getting too large, or cause her concern over an apparently poorly-developing child only to later learn that baby is the perfect size.
In an effort to encourage moms to trust the process of pregnancy and birth, and to use technology sparingly during pregnancy, I have created this summary of research regarding the usefulness and safety of ultrasounds during pregnancy. There is a lot of debate about the usefulness and safety of ultrasounds during pregnancy. Ultimately, I believe in doing the research, making an informed decision and finally, moderation in all things.
What we know for sure is that routine ultrasound use during pregnancy has not improved outcomes for birth. What this means is that women who choose to have more ultrasounds do not have better birth outcomes than women who choose limited or no ultrasounds during the pregnancy. The American College of Obstetrics and Gynecology (ACOG) has issued a statement that “no well-controlled study has yet proven that routine scanning of prenatal patients will improve the outcome of pregnancy.”
Ultrasound is the use of high frequency waves to view inside the body. It has been used regularly during pregnancy for over 20 years, and generally considered safe. Unlike x-rays, ultrasound does not use ionizing radiation, and is therefore safer than x-ray. It may be safer than x-rays, but is it harmless?
Ultrasound does have the potential to induce biological effects on the human body. The tissues in the body become heated with the application of ultrasound energy. This heating can result in cavitation which is when pockets of gas form in tissues and fluids of the body. Long-term consequences of these pockets of gas are unknown. Some studies have suggested a link between everything from left-handedness being caused by ultrasound to autism to a smaller size caused by growth plates being affected. Nothing, however, has been conclusive, and to be certain different exposures affect different people in various ways.
Present-day ultrasound machines used can emit as much as 720 mW/cm2 of acoustic output. The latest studies, done prior to 1991, which were used to demonstrate human safety, were completed with machines that emitted only 94 mW/cm2. Therefore, there is now the potential that exposure is 7 times higher than what has been studied and recommended as generally safe. (Buckley, Sarah - Gentle Birth, Gentle Mothering)
Here are some things to consider:
Researchers in New York studied 15,000 pregnant women who received ultrasound scans. They concluded that scanning provided no benefits whatsoever in any of the risk categories, such as premature babies, fetal death, multiple births, late-term-pregnancies, etc. In fact, up to this date, ultrasound scans have not revealed any information that is of clinical value. On the contrary, there is more evidence today than ever before that scans can be harmful for both the mother and the unborn child. The Association for Improvements in the Maternity Services (AIMS), England, recorded cases of women who aborted their perfectly fit and healthy babies as a result of misinterpreted scans. It is almost impossible to estimate how many women went through similar ordeals since most cases are not reported. (http://www.ener-chi.com/the-risks-of-ultrasound-scans-for-the-mother-and-the-unborn-child/)
Researchers in Finland conducted a large trial study with ultrasound. The ultrasound scans diagnosed 250 women with placenta previa in early pregnancy, a condition where the placenta lies low and therefore may prevent the baby from being born vaginally. The mothers were informed that they should expect a Caesarean section. But when it came to giving birth, only 4 women still had placenta previa. In almost all cases, the placenta moved out of the way when the womb began to grow. Ironically, the control group, which received no ultrasound scanning also had 4 women with placenta previa; all of them delivered their babies safely. (http://www.ener-chi.com/the-risks-of-ultrasound-scans-for-the-mother-and-the-unborn-child/)
Routine ultrasound scanning does not improve the outcome of pregnancy in terms of an increased number of live births or of reduced perinatal morbidity. Routine ultrasound scanning may be effective and useful as a screening for malformation. Its use for this purpose, however, should be made explicit and take into account the risk of false positive diagnosis in addition to ethical issues. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1678458/)
Transvaginal ultrasounds, done most often in the first trimester when the unborn baby is at it its most susceptible to environmental exposures, have not been tested for safety at all. The probe is covered with a condom and inserted into the vagina. This location places it closer to the developing baby, allowing a better picture, but also exposing the child to a higher frequency of ultrasound waves and therefore more temperature and risk of cavitation.
The fetal Doppler used by midwives and to trace heart patterns in doctor’s office and hospitals is also a form of ultrasound and should be used sparingly, as needed only. Exposure is best when reduced to about 3 minutes to prevent heating/cavitation and not to be done in excess. It is common for parents to now buy at-home Dopplers. While these can certainly ease anxiety by helping parents to hear their developing child, these products are not without risk.
Ultrasound use began to be used for placentography (detecting the location of the placenta in the uterus) in the 1960s. Between 1966 and 1968, this technology was improved to locate a posterior placenta. Many care providers find this information very useful.
It wasn’t until the late 1970s that ultrasounds could be used for detecting physical deformities with any amount of accuracy. The advent of color Doppler and the development of real-time scanning has improved the accuracy of ultrasounds for physical form and gestational dating, but the margin of error is still about 8%. This means that the first trimester margin or error is -/+ 5 days; at the second-trimester margin of error is -/+10 days; the third-trimester margin or error is -/+ 15.6 days. We see that as the pregnancy matures or progresses, the margin of error can be even greater than during the early weeks of pregnancy. But remember that the risks of cavitation to a first-trimester baby with a transvaginal ultrasound are higher. The general consensus is that ultrasounds performed before 24 weeks are most accurate for measuring and dating.
A study in Brisbane found that only 40% of abnormalities are detected through ultrasound. (Chan F. Limitations of Ultrasound. Perinatal Society of Australia and New Zealand 1st Annual Congress. Freemantle, Australia, 1997.)
The advent of 3D/4D ultrasound technology has created a flurry of marketing opportunities for expecting families. It is definitely true that these 3D/4D ultrasound benefit parent/baby bonding during the pregnancy but radiologists have reported that the higher resolutions from 3D/4D are rarely necessary since the 2D imaging allows adequate viewing. 3D imaging is superior for visualizing facial features like the palate but should be used sparingly and with a skilled practitioner.
In summary, the American Institute of Ultrasound Medicine has advocated for the use of medical ultrasounds performed exclusively by medical technicians. By being prudent, the recommendation is to avoid “for-fun” and keepsake ultrasounds that have become commonplace. Exercise caution if you purchase an over-the-counter ultrasound. Ultrasound use is to be done efficiently as the time of exposure is important and most OTC places provide up to 30 minutes of exposure. Ultrasounds should be completed with as low a level of output as is reasonable to achieve the needed results. Finally, ultrasounds should be completed only when clinically necessary by qualified and trained sonographers and radiologists.
I encourage each mother to look carefully about each ultrasound she is offered or considers. Too often, she is opening herself up to information that she didn’t know she would be given. This may come to her through operator error, operator opinion, or false misdiagnoses that fall within the margin of error. This can create unnecessary anxiety that some mothers still carry months and even years after a safe and healthy pregnancy is completed. Ultrasounds CAN have their time and place. Be sure to discuss your concerns with your trusted midwife, doula, or care provider.