About Birth

Ultrasound

How safe IS it?

Canadian Study Finds Pregnant Women
Having More Ultrasound Than Recommended

A study published January 4 in the Canadian Medical Association Journal found that nearly one in five women have four or more ultrasound exams in the second and third trimester.

Records of 1,399,389 women were examined with a singleton obstetric delivery during the period 1996/97 to 2006/07 in Ontario Canada. The researchers found a 55% increase in ultrasound use during the decade studied. By 2006, over one third of  women with a singleton pregnancy were having three or more ultrasound examinations during the second and third trimesters and one in five women had four or more ultrasound exams. The increased utilization did not appear to reflect changes in maternal risk.  The authors recommended efforts to promote more appropriate use of prenatal sonography.

This study is based on nearly 1.4 million deliveries in Ontario shows more than a third of women -- 37% -- now receive three or more ultrasounds in their second and third trimesters.

"While the benefits of prenatal ultrasound in high-risk pregnancies may be more clear, the value of repeat ultrasounds in low-risk patients is not," the researchers report in a study published this week in the Canadian Medical Association Journal.

Ultrasounds are widely regarded as safe. But the scans expose the fetus to a form of energy, "and there remains a theoretical risk for subtle effects on fetal development," according to the Society of Obstetricians and Gynecologists of Canada.

Moreover, as ultrasounds become increasingly sophisticated, more "incidental" and benign findings are being picked up that turn out to be nothing at all. That can cause anxiety and lead to more, and sometimes invasive tests, such as amniocentesis, where fluid is removed from the sac around the baby to look for birth defects and chromosomal problems. The procedure can lead to miscarriage.

Overall, the study found that the proportion of pregnancies with four or more second or third-trimester ultrasounds increased nearly threefold over the study period, from 6.4% in 1996, to 18.7% in 2006. The increase was more pronounced among low-risk pregnancies than high-risk ones.

The rising rates can't be explained by changes in risks to mothers or babies, the authors say. Rather, it appears non-medical reasons are behind it, including "defensive medicine" and the "entertainment value" of baby pictures.

The new study was conducted at the Institute for Clinical Evaluative Sciences (ICES) in Toronto. Researchers looked at all in-hospital deliveries from 1996 to 2006, but excluded those for multiple births, such as twins or triplets, "where ultrasounds are used often, for very good reasons," said principal investigator Dr. John You, an assistant professor of medicine at McMaster University in Hamilton and ICES scientist.

Next, they looked at Ontario Health Insurance (OHIP) claims to count the number of ultrasounds per pregnancy, on a year-by-year basis. The rate increased 55% over the 10-year study period.

"A 55% increase is pretty substantial. Most things don't increase by that much over a 10-year period," Dr. You said.

The study used Ontario data only, "but I certainly don't think we've seen a decrease over time in any other provinces," Dr. You said. "I wouldn't be surprised if we saw similar findings across the country."

The finding held even after researchers took the mother's age, rates of diabetes, high blood pressure and other factors into account.

Obstetricians practice in a high-risk malpractice environment; they're sued more often than any other kind of doctor.

"Obstetricians may feel pressure to provide reassurance to their patients with a fairly inexpensive and safe test," You said.

But Dr. You said the downside of so many ultrasounds is cost and anxiety.

"We're not arguing at all that ultrasounds are being overused in complicated, high-risk situations where there's pretty clear benefit from it," Dr. You said. "But, we're seeing lots of people getting four, five, six ultrasounds" for uncomplicated pregnancies.

View the CMAJ Study Abstract HERE
_____________________

Although ultrasound has been around since the late 1950's, it wasn't widely accepted as a safe form of examination until the 1980's.  Because the wide spread use of ultrasound is more recent, it is possible that there are long term risks that have not been discovered. 

Ultrasound machines measure the heat and mechanical measurements being used by the machine to assist technicians in minimizing risks to the fetus and mother.  The downside is that precise safety levels for ultrasound machines have not been established, therefore leaving a possibility for a technician to use high levels that are not required. 

"Although there are no known risks of ultrasound imaging and heartbeat monitors, the radiation associated with them can produce effects on the body," says Robert Phillips, Ph.D., a physicist with FDA's Center for Devices and Radiological Health (CDRH).  "When ultrasound enters the body, it heats the tissues slightly.   In some cases, it can also produce small pockets of gas in body fluids or tissues."  (Cavitation)

Anne Frye, author of "Understanding Diagnostic Tests in the Childbearing Year", says one minute of Doppler exposure is equivalent to thirty-five minutes of an imaging scan (because Dopplers use continuous ultrasound instead of pulsed ultrasound)

Midwife Apprentice Liz listening to Michelle's baby with a fetoscope.

Until the early 1990's, midwives primarily used fetoscopes to assess fetal heart variability during pregnancy and labor.  (Fetoscopes are Fetal Stethoscopes.)  Even when hand held ultrasound dopplers became more readily available, most midwives still used a fetoscope during prenatal care, minimally using the doppler when needed.  Today, midwives who embrace the possible  risks of ultrasound have continued to nurture and maintain the skill of using  a fetoscope, limiting the use of ultrasound dopplers to times of need.

Ultrasound can be beneficial when used wisely.   But what are the safe limits of ultrasound use and how much are we overusing it?  As a society we are using ultrasound regularly and many practitioners don't even question it,  it's cool to hear the baby's heart out loud and to glimpse into the womb to see the growing baby.  Is it really necessary, however, to routinely check a baby's heart with doppler ultrasound when there are other, less invasive options such as the fetoscope? Are we using ultrasound more for entertainment than as a result of medical indication?  Are families truly making INFORMED choices where ultrasound is concerned?  This topic begs for further study and discussion so that consumers can know exactly what they are asking for when they choose ultrasound.

Lisandrea listening to her own baby's heart with a fetoscope.

We welcome your opinions, send your comments to:   newsletter@charischildbirth.org   Let's study together!

To Health, Wisdom and God's presence in our walk as midwives, doctors and birthing families!
~Susan Oshel

The following resources will further enlighten the curious mind!

Ultrasound - by Beverley Lawrence Beech

On The 'Safety' and 'Usefulness' of Prenatal Ultrasound

The Dangers of Prenatal Ultrasound

How Ultrasound Works

Ultrasound Scans May Harm Unborn Babies

Ultrasound Scans Linked to Brain Damage in Babies