Back to Table of Contents | December 2009

Pulse

Necessity or Expectation?

Some studies say routine obstetric ultrasound does not improve outcomes. But many obstetricians defend its value.

Getting an ultrasound during the first 18 to 20 weeks of pregnancy has become almost as commonplace as attending birthing classes. Most women look forward to viewing the shadowy-white, pulsing images. But while ultrasound has become popular with parents during the last 15 years, there’s little evidence that it leads to better outcomes. As the health care reform debate picks up steam at both the federal and state levels, that lack of data is leading some to question the need for routine ultrasound during pregnancy.

In a low-risk pregnancy, the purpose of the screening ultrasound is to confirm the viability of the pregnancy and the number of fetuses, estimate gestational age and amniotic fluid volume, evaluate the position of the placenta, assess cardiac activity, and screen for fetal anomalies such as cardiac, kidney, or brain defects, and chromosomal abnormalities such as trisomy 13 or trisomy 18, which are incompatible with life. According to the American College of Obstetrics and Gynecology (ACOG), these routine, two-dimensional ultrasounds are safe for both fetus and mother. But ACOG does not dispute the possibility that ultrasound could be harmful if used repeatedly. In its February 2009 Practice Bulletin on ultrasonography in pregnancy, the academy cautioned that “ultrasound energy delivered to the fetus cannot be assumed to be completely innocuous, and the possibility exists that such biological effects may be identified in the future.”

What the Research Shows

Although the benefits of ultrasound may be anecdotally apparent to physicians and patients, the evidence as to whether it leads to better clinical outcomes is inconclusive. In one review article published in Prenatal Diagnosis in 2002, the technology’s sensitivity for detecting fetal anomalies was estimated to range from 13.3 percent to 82.4 percent, with ultrasound screenings performed at tertiary centers having higher detection rates. Another notable study published in the New England Journal of Medicine in the mid-1990s reviewed ultrasound data from 15,151 low-risk pregnant women who were randomly assigned to receive either routine screening ultrasound or ultrasound for medical reasons only. No significant difference in outcomes was detected between the two groups.

The problem with such studies, notes Janette Strathy, M.D., an obstetrician with Park Nicollet Health Services in St. Louis Park, is that adverse outcomes are typically (and in the case of the New England Journal of Medicine article) defined as fetal death, neonatal death, or neonatal morbidities such as heart defects. “When you think about the fact that ultrasound is used to detect or diagnose a birth defect, that baby is going to have that birth defect whether you do the ultrasound or not, so yes, there is no change in outcome,” she says. “But there is certainly a change in the ability for the physician to manage the pregnancy better—and for the parent to prepare for a child with special needs.”

Doug Creedon, M.D., Ph.D., a Mayo Clinic obstetrician, agrees. “Is there evidence that it affects outcomes? No. However, is there evidence that ultrasound can be useful for detecting fetal anomalies? Absolutely. And is that important for patients being able to make informed decisions? Again, I would say absolutely.”

An Eye on Cost

Sue Crook, M.D., a radiologist with Suburban Radiologic Consultants in the Twin Cities, believes the bigger issue underlying the increased attention to the lack of evidence about ultrasound is cost. Having been in practice for more than 15 years, she often has noticed physicians ordering far more ultrasounds for their patients than a single screening ultrasound at 18 or 20 weeks.

One reason is because women are learning that they are pregnant much earlier than they did when she was starting practice. “They get into their ob/gyn’s office right away and get a really early ultrasound for dating—rather than just waiting to 11 to 12 weeks to see their doctor once they know they are pregnant. So they are getting that first early ultrasound, which a lot of times is so early that we cannot confirm that it’s a viable pregnancy. Then they come back for two or three more ultrasounds until we can see the little heartbeat,” she says.

Another reason why some physicians may order more ultrasounds is to protect themselves legally. As a member of the claims committee for Midwest Medical Insurance Company, Crook knows that the absence of frequent ultrasounds can be used as evidence in a malpractice suit. “In a lot of these claims, the suing team will use ultrasound against the doctor. They’ll say, for example, that if the physician would have done an ultrasound, they would have known that the patient would be delivering a big baby, and they could have prevented a shoulder dystocia,” she says, adding that tort reform could go a long way toward changing this practice and, thus, reducing the cost of obstetric care. “I don’t fault the obstetricians. It’s just the environment in which they are practicing,” she says.

In addition to tort reform, Crook would like to see screening ultrasound used more effectively—at 11 to 13 weeks, rather than 18 to 20. She says 11 to 13 weeks is the time when gestational dating is more accurate and a nuchal translucency scan, a more cost-effective test than screening ultrasound, can be performed to assess for gestational age, cardiac activity, and chromosomal abnormalities.

The cost of obstetrical care is being addressed by the Minnesota Department of Health in a payment reform measure known as “baskets of care.” Baskets of care are bundles of services associated with a particular condition such as pregnancy. Insurers would pay for a bundle rather than for each individual procedure or service necessary for treating the condition, thus keeping costs in check. On June 22, 2009, a working group, under the leadership of the Institute for Clinical Systems Improvement (ICSI), submitted to the Department of Health their recommendations for what prenatal care should encompass for a woman with a confirmed, single intrauterine pregnancy. They acknowledged that there was no evidence to support ultrasound in the first trimester, but they avoided recommending that routine ultrasound be abandoned altogether: “It has become the standard of care to offer it, and it is a patient expectation,” the report reads.

Evidence Meets Experience

For many physicians, the enactment of cost-control measures such as tort reform or bundled care is unlikely to change the way they practice. As a member of the obstetrics basket-of-care working group, Creedon says the lack of data about outcomes prompted nonobstetricians in the group to question whether routine ultrasound during pregnancy is necessary, but he advocated staunchly for its inclusion. “In my professional opinion, the potential benefit for identifying problems with the fetus far outweighs the risk of a false-negative,” he says. If the standard ultrasound were eventually to be cast from the obstetrics basket, Creedon says he would continue to offer the screening to expecting mothers. “I would still offer it to patients, and they would have to decide whether they should pay for it,” he says. “I simply believe too strongly that it’s beneficial.”

Park Nicollet’s Strathy says she, too, will continue to recommend screening ultrasound. When she started practicing 25 years ago, ultrasound was not routinely recommended for pregnant women. A few years into her practice, she delivered a baby with encephaly, a fatal birth defect that could have been detected on a routine ultrasound. She never forgot the parents’ sadness in discovering the problem at birth. Had she offered them a routine ultrasound, Strathy says, they could have considered terminating the pregnancy or prepared for the fact that their baby would not live. “I changed my mind about ultrasound immediately after that,” she says. “I don’t care what insurance says. I don’t care what my colleagues do. I will always offer the patient an ultrasound, and if they choose not to have it, at least I know that I have done the best I can.”—Jeanne Mettner