Ultrasound in Pregnancy

Ultrasound in America 

The use of ultrasound in obstetrics has become routine at the first prenatal office visit to establish a due date rather than using the mother’s last menstrual period date, conception date, or other clinical findings that healthcare providers relied upon before such technology was implemented. Some providers use ultrasound at each office visit to visualize the fetal heartbeat and so the mother can enjoy seeing her baby. However, this results in many healthy, low risk women having up to 10 ultrasounds in the course of their pregnancy. Since ultrasound was originally intended for high-risk clients, we should consider why ultrasound technology is routinely being used on healthy, low-risk women – how much is too much?

According to ACOG (American College of Obstetrics and Gynecologists), “in a population of women with low-risk pregnancies, neither a reduction in perinatal morbidity and mortality nor a lower rate of unnecessary interventions can be expected from routine diagnostic ultrasound. Thus ultrasound should be performed for specific indications in low-risk pregnancy.” In English, this means that routine ultrasounds don't equal better outcomes or fewer interventions. So what is the benefit you may ask? Read on. 

What is ultrasound?

Ultrasound is a form of high-frequency energy (approximately 100 times the frequency of normal sound waves) that forms an image of the baby by reflecting waves off the baby’s tissues and onto a receptor probe. The contact of ultrasound waves compresses tissue. The result of the tissues absorbing ultrasound energy and of being compressed is a temperature increase on the cellular level. The increase in temperature combined with pressure may result in cavitation (the forming of gas bubbles) and implosion of cell membranes. It is important to remember that no well-controlled scientific investigations are currently being done or have ever been done to determine the long-term risks of ultrasound use.


Medical vs non-medical ultrasound

It is important to distinguish between ultrasounds that are used to ascertain medical information and those that are performed for the entertainment of the parent(s).  In cases of medical necessity, the information gained from ultrasound can be invaluable in decision-making.  There are many medically pertinent reasons to have an ultrasound during your pregnancy, including:

  • Calculating gestational age in the first trimester when last menstrual period date is not known and other methods are uncertain. The dating ability of ultrasound becomes less accurate as the pregnancy progresses
  • Examining the fetus for abnormalities
  • Screening for certain genetic conditions, such as Downs syndrome, Trisomy 18, and others
  • Locating the position of the placenta and determining the type of umbilical cord insertion
  • Determining fetal position if palpation is inconclusive
  • Follow up for screen positive findings 

Reasons for ultrasound that are not considered medically necessary include:

  • Determining the sex of the baby
  • Seeing what the baby looks like
  • 4D “keepsake” videos

 The most recent statement from the FDA regarding “keepsake ultrasound” is as follows:

“The long-term effects of tissue heating and of the formation of partial vacuums in a liquid by high-intensity sound waves (cavitation) are not known. When the product (keepsake ultrasound) is purchased over the counter and used without prior consultation with a health care professional, there is no oversight of how the device is used and little or no medical benefit derived from the exposure. The number of sessions or the length of a session to which a fetus is exposed is uncontrolled, thus raising the potential for harm to the fetus.”

In other words, please don't get keepsake ultrasounds. (I'm sure I'm making a lot of friends with all the ultrasound boutiques right about now)

  Medical Indications for ultrasound by trimester

First trimester

  • Confirm intrauterine pregnancy, presence of the gestational sac and embryo
  • Assess number of embryos
  • Determine the presence of cardiac activity
  • Confirm gestational age by measuring crown-rump length and looking for anatomical markers
  • Diagnose a fetal demise
  • Nuchal translucency marker to screen for genetic disorders

Second trimester

  • Examine fetus for abnormalities - which may reveal conditions that are inconsistent with life outside the womb and only detectable by ultrasound. Ultrasound may also reveal a life-threatening abnormality that could only be corrected with immediate access to hospital resources.
  • Assess fetal lung maturity
  • Determine cervical length
  • Locate placenta
  • Assess amniotic fluid volume

Third trimester

  • Follow up monitoring of placental position
  • Assess amniotic fluid volume
  • Assess fetal growth
  • As part of a non-stress test or biophysical profile
  • Determine fetal position if palpation is inconclusive 

What do you do with the information?

Ultrasound gives valuable information to parents and providers as they proceed with a plan of care. As with many of the tests and screens offered in the course of your pregnancy, it is important to consider what you would do with the information gained via ultrasound. Would seeing your healthy baby give you a peace of mind that you would otherwise be without? Would knowing your baby has a condition change your plans for your pregnancy and birth time? The answers to these questions and others may help determine the timing of and the purpose for the ultrasounds you want. 

Please note that the information above is intended to be informative and not a replacement for medical care. Please contact your care provider if you have any questions or concerns regarding ultrasound or fetal monitoring.