By Elizabeth Bruce
Issue 102, September/October 2000
Ultrasounds are commonly recommended by doctors, especially for "high-risk" mothers--a category that often includes women over 35 or under 18 years of age, diabetic mothers, women who were previously infertile, and even those who have miscarried before. In other words, virtually every pregnant woman will at some point be offered an ultrasound examination.
The two main concerns that most women will likely have about ultrasound regard its safety and accuracy--two issues about which, unfortunately, women receive little information. In reality, ultrasound is not sound at all. Sound is between 20 hertz and 20 kilohertz. Ultrasound waves travel between 2 and 4 megahertz and have been classified by the Bureau of Radiological Health as "radiation."1
What is commonly thought of as ultrasound is, in fact, the scanner. There are three types of ultrasounds: scanning devices, doptones, and external fetal monitors (EFMs). During my first pregnancy, it was never pointed out to me that the innocuous-seeming doptone was, in fact, using ultrasound. Nor did I realize that the EFM employed ultrasound. In subsequent pregnancies, my midwives informed me about ultrasound's possible dangers, and offered to use a stethoscope or fetascope. Obstetricians, unfortunately, all too often reassure their patients that these machines are harmless. Some concerned mothers who ask that a stethoscope be used instead are considered hysterical or at least terribly backward. Yet it is always the woman's prerogative to decide whether she and her unborn child will be exposed to potentially harmful ultrasound waves.
What Are the Current Indications for Ultrasound?
The doppler is the small, hand-held device most often used at each prenatal visit after the tenth week (LMP) to listen to the baby's heartbeat. Fortunately, the doppler's exposure time is the shortest, making it potentially the least damaging ultrasound device.
The longest exposure occurs with EFM. Every woman who has birthed in a hospital is probably familiar with EFM monitoring--a belt is strapped to the laboring woman, either intermittently for 20-minute segments out of an hour or continuously. With EFM, there does not have to be an indication per se--besides the fact that the woman is laboring in the hospital. EFM use for low-risk women skyrocketed from 47 percent in 1980 to 76 percent in 1988, while its use increased only moderately for high-risk patients (43 percent to 56 percent) during the same years, possibly because of economic reasons.2 The cost of EFM, an understandably expensive procedure, is borne by insurance companies, and ultimately, US consumers.
Ultrasound scans are employed during any stage of pregnancy for a variety of reasons, including confirmation of EDCs (estimated date of confinement, or delivery), confirmation of multiple pregnancy, detection of small-for-dates babies, assessment of fetal maturity, or verification of suspected breech position. Scans are also used in relation to medical interventions such as external cephalic version (attempt to manually turn a breech baby), dystocia (slow to progress labor), late labor, cervical cerclage (suturing of a cervix that is too dilated too early in pregnancy), premature rupture of membrane (breaking the waters), or before cesarean section. Ultrasound scans are also indicated in the case of postdate pregnancy, to locate the baby's position before an amniocentesis is performed or to detect placental problems.
1. L. L. Albers and C. J. Krulewitch, "Electronic Monitoring in the United States in the 1980s," Obstetrics and Gynecology 82 (July 1993): 8-10.
2. "Ultrasound: Is It Safe?" Utah Midwives Newsletter (1991): 4-6.
Elizabeth Bruce, MA, CCE, is a Birth Works facilitator. She currently stays home with her four children, ages 2, 5, 7, and 9. Her youngest two children were born at home, ultrasound-free.