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Long before their baby is born, expecting parents come back from the doctor's office with a picture fit to be framed: a sonogram image of the fetus taken by an ultrasound procedure.
A sonogram is not only a memento but also a valuable diagnostic tool, periodically performed during the nine months of a pregnancy to monitor the baby's growth. In addition, states increasingly are passing legislation requiring a woman who wants an abortion to have ultrasound and to be given the chance to view the image of the fetus.
Although ultrasound is a pain-free, low-cost and non-invasive imaging process that does not involve radiation, the American Institute of Ultrasound in Medicine, the American College of Radiology and the American College of Obstetricians and Gynecologists recommend restraint. In a joint guideline, the groups say “this diagnostic procedure should be performed only when there is a valid medical indication, and the lowest possible ultrasonic exposure setting should be used to gain the necessary diagnostic information.”
During an ultrasound procedure, a handheld device called a transducer uses sound waves with an extremely high frequency (over 20,000 vibrations per second) to check the development of the fetus in the womb. Because ultrasound does not work correctly through air, the ultrasound technician puts a clear gel on the woman's abdominal region and places the transducer on the target area. The sound waves reflect from bones, tissues and organs, carrying signals back to a computer, creating ultrasound pictures.
Ultrasound is used throughout the pregnancy to monitor the condition of the woman and the fetus. It is performed during the first trimester to confirm the pregnancy and then to determine a heart rate, set a likely birth date, check to see if there is more than one fetus, measure the baby's head and gauge the chances of a miscarriage or determine if there are any issues with the cervix, uterus or placenta. Ultrasound also can reveal the development of an ectopic pregnancy, in which the fertilized ovum develops outside the uterus.
During ultrasound procedures in the second and third trimesters, doctors not only can monitor the baby's health, positioning and growth but also can see if it has birth defects or placenta previa, in which the placenta is implanted in the lower part of the uterus, causing bleeding. Detecting problems early allows doctors and patients to plan for the most favorable outcome possible.
While ultrasound of a fetus produces no known negative side effects, researchers say they cannot be completely ruled out. In a paper published in August, three scientists from the U.S. Food and Drug Administration (FDA) warn that “ultrasound energy delivered to the fetus cannot be regarded as completely innocuous.” They point to studies that show ultrasound can produce vibration and a rise in tissue temperature.
Other researchers caution that current ultrasound technology “has significantly higher output potential than older machines used in most clinical studies” and that the safety profile for modern machines is unknown. Some advocacy groups have even speculated that the increased use of fetal ultrasound has contributed to the rise in autism, although a journal article published a year ago found no such correlation.
Proud prospective parents who might be tempted to purchase a “keepsake ultrasound video” from a private company should also think twice. One such company says “it's a great way to preserve the memory of this special time shared with your child for years to come” and encourages parents to come “as often as you wish.”
But the FDA strongly recommends against videos. “In some cases, the ultrasound machine may be used for as long as an hour to get a video of the fetus,” says the FDA. “We are concerned about this misuse of diagnostic ultrasound equipment.” A little more than a year ago, Connecticut banned keepsake ultrasounds.
— Barbara Mantel and Caroline Young
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