Correspondence
Prenatal Ultrasound Screening and Perinatal Outcome
N Engl J Med 1994; 330:570-572February 24, 1994
- Article
To the Editor:
Ewigman et al. (Sept. 16 issue)1 attempted to determine the efficacy of ultrasonography in pregnancy, but their methods obscured the issue of routine scanning. Of 55,744 women registering for obstetrical care, the authors excluded 32,317 (58 percent). Another 7897 (14 percent) were lost to follow-up or declined to participate in the study. Thus, of all the women, only 15,530 (28 percent) were actually studied. Of the half assigned to the control group (14 percent of the initial cohort), 45 percent underwent ultrasonography.
The authors provided no data to explain why the women in this group underwent scanning. It appears that ultrasonography, even in selected low-risk women, is deemed important enough to be used often for patient care. The fact that the outcomes in the routine-ultrasonography group and the control group were similar is not surprising, because so many of the women in the control group underwent scanning. Thus, because of its wide-ranging exclusions and the use of ultrasonography in an ill-defined manner in the control group, the study cannot clarify the role of ultrasonography in obstetrics. It is false economy to establish a long list of indications for ultrasonography, encompassing most pregnancies, and not recommend the approach on a universal basis.
1 ReferencesSteven H. Golde, M.D.
St. Joseph Medical Center, Burbank, CA 91505-48661
Ewigman BG ,Crane JP ,Frigoletto FD , et al. Effect of prenatal ultrasound screening on perinatal outcome. N Engl J Med 1993;329:821-827
Full Text | Web of Science | Medline
To the Editor:
Ewigman et al. report that routine ultrasound screening is not worthwhile for the detection of fetal anomalies and other problems of pregnancy. Unfortunately, the authors fail to substantiate this claim with respect to fetal anomalies. Their end point of adverse perinatal outcomes, as defined in Table 2 of the study, does not include major anomalies unless certain events occurred in the intensive care nursery. Indeed, most pregnancies involving major fetal anomalies (213 of 350) were not considered to have an adverse outcome, even though almost all the anomalies (199 of 213) were discovered too late to allow the option of termination. Thus, any long-term savings in cost and in the social impact of these anomalies -- if properly detected -- is not considered.
The sensitivity of 16.6 percent for the sonographic detection of major anomalies before 24 weeks of gestation appears to be quite low, as compared with the reported sensitivity of 14 to 78 percent in other studies1,2. Unfortunately, the authors do not specify the anomalies missed in order to allow the reader to judge whether they should have been detected.
Perhaps the low sensitivity of scanning before 24 weeks of gestation is related to the apparent inexperience of the many clinicians performing ultrasonography in this study. The minimum of 25 supervised examinations required of a sonologist in order to participate is remarkably low. Evidently, many of the sonologists had no previous experience in the detection of many or all of the numerous anomalies they were seeking.
The authors further indicate that even if the rates of early detection (<24 weeks of gestation) of fetal anomalies had been satisfactory, it would not have mattered, since only a minority (33 percent) of the 39 women whose fetuses had a major anomaly chose to terminate their pregnancies. However, these results are contradicted by a previous study in which 67 percent of 113 women with fetuses with anomalies detected before 23 weeks of gestation and only 14 percent of 222 women with fetuses with anomalies detected after 23 weeks chose to terminate their pregnancies2.
Future studies should consider anomalies separately, rather than as part of a confusing mixture of perinatal outcomes, regard them as the adverse outcomes they are, and consider their long-term social and economic consequences rather than just their perinatal effect.
2 ReferencesFrederick N. Hegge, M.D.
Emanuel Hospital, Portland, OR 972271
Levi S ,Hyjazi Y . Sensitivity of routine ultrasonographic screening for congenital anomalies during the last 5 years. J Ultrasound Med 1992;11:188-188
Web of Science | Medline2
Hegge FN ,Franklin RW ,Watson PT ,Calhoun BC . An evaluation of the time of discovery of fetal malformations by an indication-based system for ordering obstetric ultrasound. Obstet Gynecol 1989;74:21-24
Web of Science | Medline
To the Editor:
The study by Ewigman et al. raises the provocative question of the benefits of routine ultrasonography in terms of perinatal outcome. The media drew the expected amount of attention to the article and its conclusions, in part perhaps because of the simultaneous release of the Clinton health plan. The failure of the study to find a benefit cannot be taken at face value.
The definitions of adverse perinatal outcome used were primarily related to complications of prematurity -- that is, neonatal death, retinopathy of prematurity, bronchopulmonary dysplasia, need for mechanical ventilation, necrotizing enterocolitis, and intraventricular hemorrhage. Nowhere has it been suggested that ultrasonography may prevent these complications, so the conclusions of the study in this area are hardly surprising.
More troubling is the conclusion that the routine use of ultrasonography added 1.6 scans per pregnancy. Forty-five percent of the women assigned to the group scheduled to undergo ultrasonography only for medical indications had at least one sonogram. Therefore, 72 percent of the 15,530 women studied had one or more sonograms. The calculation of added costs for routine sonograms should be confined to the 28 percent of women who had no sonograms. Using the same cost calculations as the authors brings the incremental cost to below $350 million. On the basis of the low rate of detection of fetal anomalies in this study, centralized fetal scanning in dedicated obstetrical units would be expected to improve cost effectiveness through better detection of fetal anomalies, potentially at even lower costs.
Joshua A. Copel, M.D.
Yale University School of Medicine, New Haven, CT 06520-8063Lawrence D. Platt, M.D.
Cedars-Sinai Medical Center, Los Angeles, CA 90048Stuart Campbell, M.D.
Kings College Hospital, London SE5 8RX, United KingdomTo the Editor:
Although the routine use of ultrasound screening does not appear to improve the outcome of pregnancy,1 it is possible to justify a streamlined protocol for routine screening on the basis of its contribution to prenatal biochemical screening. This justification requires that the use of ultrasound screening be limited to counting the number of fetuses and determining gestational dates. When these dates are based on the first day of the last menstrual period, approximately 15 percent are incorrect by more than two weeks. As of mid-1992, 2.1 million of the 4.2 million women who become pregnant each year in the United States were undergoing biochemical screening for the open neural-tube defects and Down's syndrome in their fetuses2.
Accurately interpreting the results of biochemical screening requires reliable gestational dates. A protocol for routine ultrasound screening as described above would reduce by half the number of pregnancies that would be initially classified as being at high risk according to prenatal biochemical-screening measurements3,4. The main benefit of this approach would be a substantial reduction in the number of women made unnecessarily anxious and an acceleration of the subsequent diagnostic process for those with abnormal screening results. In addition, an occasional case of open spina bifida or Down's syndrome would be detected by biochemical screening that would otherwise be missed because of incorrect dating.
4 ReferencesJames E. Haddow, M.D.
George J. Knight, Ph.D.
Glenn E. Palomaki, B.S.
Foundation for Blood Research, Scarborough, ME 040741
Ewigman BG ,Crane JP ,Frigoletto FD , et al. Effect of prenatal ultrasound screening on perinatal outcome. N Engl J Med 1993;329:821-827
Full Text | Web of Science | Medline2
Palomaki GE, Knight GJ, McCarthy J, Haddow JE, Eckfeldt JH. Maternal serum screening for fetal Down syndrome in the United States: a 1992 survey. Am J Obstet Gynecol (in press).
3
Wald NJ ,Cuckle HS ,Densem JW ,Kennard A ,Smith D . Maternal serum screening for Down's syndrome: the effect of routine ultrasound scan determination of gestational age and adjustment for maternal weight. Br J Obstet Gynaecol 1992;99:144-149
CrossRef | Medline4
Haddow JE ,Palomaki GE ,Knight GJ , et al. Prenatal screening for Down's syndrome with use of maternal serum markers. N Engl J Med 1992;327:588-593
Full Text | Web of Science | Medline
Author/Editor Response
The authors reply:
To the Editor: We agree with Dr. Golde that prenatal ultrasonography is often useful. We found, however, that when physicians ordered sonograms as needed, the perinatal outcome was similar as with a policy of two routine screening sonograms and involved far fewer tests.1 Women were excluded from the study mainly because their physicians thought a sonogram was indicated. The most common reasons for exclusion were a previous sonogram (12.4 percent), an unknown date of the last menstrual period (9.6 percent), and a gestational age of more than 18 weeks (6.6 percent).
All the sonologists in our study were experienced. The requirement that the first 25 scans performed be reviewed was a quality-control measure, not the minimal experience required of a sonologist. Our use of registered diagnostic medical sonographers, the selection of experienced radiologists and maternal-fetal specialists as sonologists, and our rigorous quality-control program probably led to higher-quality ultrasonography than is generally available in the United States.
Dr. Hegge's letter raises critical issues about the detection of anomalies. We are preparing a manuscript describing the anomalies; briefly, we detected anomalies with an accuracy similar to that reported in published studies.
The cost estimate by Copel and colleagues erroneously assumes that the women in the control group who underwent scanning had the same number of scans as the women in the screened group. The screened group had 2.2 sonograms per woman, as compared with 0.6 sonogram per woman in the control group -- a difference of more than threefold. Fifty-five percent of the women in the control group had no sonogram, and an additional 33 percent had only one sonogram.
The proposal by Haddow and colleagues that ultrasound screening could be justified on the basis of its contribution to prenatal biochemical screening is not supported by our findings. For example, only 220 scans were performed in 7718 women in the control group because of abnormal maternal serum alpha-fetoprotein concentrations. Performing 7718 scans for screening purposes when only 220 are necessary would be hard to justify.
Some readers were confused by the phrase describing the documentation of ultrasonography “by x-ray or thermal images.” Some ultrasound images were captured on x-ray film; we did not use radiography in any fetuses.
1 ReferencesBernard Ewigman, M.D., M.S.P.H.
University of Missouri-Columbia, Columbia, MO 65212James P. Crane, M.D.
Jewish Hospital at Washington University, St. Louis, MO 63110Fredric Frigoletto, M.D.
Brigham and Women's Hospital, Boston, MA 02115for the Routine Antenatal Diagnostic Imaging with Ultrasound Study Group
1
LeFevre ML ,Bain RP ,Ewigman BG ,Frigoletto FD ,Crane JP ,McNellis D . A randomized trial of prenatal ultrasonographic screening: impact on maternal management and outcome. Am J Obstet Gynecol 1993;169:483-489
Web of Science | Medline
- Citing Articles (1)
Citing Articles
1
Jun Zhang, James Troendle, Susan Meikle, Mark A. Klebanoff, William F. Rayburn. (2004) Isolated oligohydramnios is not associated with adverse perinatal outcomes. BJOG: An International Journal of Obstetrics and Gynaecology 111:3, 220-225
CrossRef
