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ORIGINAL RESEARCH
Impact of New Society of Radiologists in Ultrasound Early First-Trimester Diagnostic Criteria for Nonviable Pregnancy Maowen Hu, MD, Liina Poder, MD, Roy A. Filly, MD
Objectives—New early first-trimester diagnostic criteria for nonviable pregnancy recommended by the Society of Radiologists in Ultrasound via a multispecialty consensus panel extended the diagnostic size criteria of crown-rump length from 5 to 7 mm for embryos without a heartbeat and mean sac diameter from 16 to 25 mm for “empty” sacs. Our study assessed the potential impact of the new criteria on the number of additional follow-up sonograms these changes would engender. Methods—A retrospective study of all first-trimester sonograms in women with first trimester bleeding from 1999 to 2008 was conducted. Everyone included in the study had a visible gestational sac in the uterus. There were no pregnancies of unknown location or ectopic pregnancies included in this study cohort. Pregnancy of unknown location was used to describe cases in which there were no signs of pregnancy inside or outside the uterus on transvaginal sonography despite a positive pregnancy test result. A total of 1013 patients met the inclusion criteria. Results—Seven hundred fifty-two patients (74%) had identifiable embryos, and 261 (26%) did not. Of those with an identifiable embryo, 286 (38%) had no detectable embryonic cardiac activity. The breakdown of crown-rump lengths in this group was as follows: 100 measuring less than 5 mm, 36 measuring 5 to 7 mm, and 150 measuring 7 mm or greater. The breakdown of mean sac diameters in those without a visible embryo was as follows: 120 measuring less than 16 mm, 90 measuring 16 to 25 mm, and 51 measuring 25 mm or greater. Conclusions—When diagnosing a failed pregnancy, there can be no room for error. Only 126 of 1013 early pregnancies threatening to abort (12%) fell into the more conservative zones defined by the new compared to the former size criteria (crown-rump length, 5–7 mm; mean sac diameter, 16–25 mm). Therefore, the potential impact of the new guidelines on follow-up sonograms does not appear inordinate. Key Words—bleeding; embryo; nonviable; obstetric ultrasound; sonography; threatened abortion; ultrasound education Received November 28, 2013, from the from the Department of Radiology, University of California, San Francisco, California USA. Revision requested December 9, 2013. Revised manuscript accepted for publication December 28, 2013. Address correspondence to Liina Poder, MD, Department of Radiology, University of California, 505 Parnassus Ave, PO Box 0628, San Francisco, CA 94143-0628 USA. E-mail: [email protected] doi:10.7863/ultra.33.9.1585
S
onography plays a pivotal role in the evaluation of women who are bleeding in the first trimester of pregnancy. A variety of sonographic features have been studied in the literature for trying to identify early pregnancy failure.1–3 The criteria most often used to diagnose pregnancy failure include absence of cardiac activity by a certain crown-rump length and no visible embryo by a certain mean gestational sac diameter. However, there are variations in cutoff values for mean sac diameter and crown-rump length used to define pregnancy failure by different observers and approved by
©2014 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2014; 33:1585–1588 | 0278-4297 | www.aium.org
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Hu et al—New Early First-Trimester Diagnostic Criteria for Nonviable Pregnancy
different organizations (most notably the American College of Radiology and the Royal College of Obstetricians and Gynaecologists). In the most common criteria used in the United States, no follow-up sonogram was recommended for patients showing an embryo with a crownrump length of 5 mm or greater and no heartbeat or for gestational sacs measuring 16 mm or greater in mean sac diameter and lacking an embryo.4–6 However, a recent meta-analysis of previous data showed that there is a substantial likelihood that 5-mm crown-rump length and 16-mm mean sac diameter cutoffs result in false-positive diagnoses, which place normal intrauterine pregnancies at risk for inappropriate termination.7 Recent studies involving many more patients also reported several cases of embryos with a crown-rump length of 5 to 6 mm and no heartbeat or a mean sac diameter of 17 to 21 mm (interobserver variability, 17–25 mm) and no visible embryo that subsequently proved to be viable pregnancies.7–10 Incorrect diagnosis of pregnancy failure can prompt interventions that interrupt a pregnancy that otherwise would have had a normal outcome. To minimize or avoid false-positive test results, more stringent diagnostic criteria for nonviability by expanding the crown-rump length cutoff to 7 mm for embryos without a heartbeat and the mean sac diameter cutoff to 25 mm for “empty” sacs was recently recommended by a Society of Radiologists in Ultrasound multispecialty consensus panel.11 Although these more conservative new criteria will potentially lead to a diminishingly small number of false-positive diagnoses of nonviable pregnancy, they also raise the question of the effect they will have on increasing the number of followup sonograms. Our study was designed to address the latter issue.
Materials and Methods A retrospective review of all sonograms from women who had bleeding or “spotting” in the first trimester and were scanned at the University of California San Francisco Medical Center in the 10 years from 1999 to 2008 was undertaken. A total of 1028 initial sonographic examinations were performed during this period. Follow-up examinations were excluded. However, the initial sonograms of different pregnancies in the same woman were included. Of these 1028 initial examinations, 15 of the sonograms were irretrievable at the time of the review and were excluded. Therefore, a total of 1013 sonograms were included in this study. Everyone included in the study had a visible gestational sac in the uterus. There were no pregnancies of unknown location or ectopic pregnancies included in this
1586
study cohort. Pregnancy of unknown location was used to describe cases in which there were no signs of pregnancy inside or outside the uterus on transvaginal sonography despite a positive pregnancy test result. Each patient was scanned with both transabdominal and endovaginal techniques (Acuson Sequoia; Siemens Medical Solutions, Mountain View, CA) by a sonographer according to the University of California San Francisco protocol. Transabdominal transducers used included vector arrays with selectable frequencies ranging from 1 to 4 MHz and curved arrays with selectable frequencies ranging from 2 to 6 MHz. The endovaginal transducer used was a tightly curved array with selectable frequencies from 4 to 8 MHz. The reports of these sonograms were reviewed for the presence or absence of an embryo/fetus, presence or absence of a heartbeat if an embryo/fetus was observed, and mean sac diameter if no embryo/fetus was observed. If an embryo was seen, then the crown-rump length was measured in millimeters to the nearest 10th of a millimeter. The mean sac diameter was measured in millimeters, again to the nearest 10th of a millimeter. Follow-up was not undertaken to determine the outcomes of these pregnancies. The University of California San Francisco Committee on Human Research approved this study.
Results Of the 1013 first-trimester sonograms obtained from women with bleeding or spotting in the first trimester, 752 (74%) showed an identifiable embryo, and 261 (26%) had no identifiable embryo within the visible gestational sac (Figure 1). Of those with an identifiable embryo, embryonic cardiac activity was detected in 466 (62%) and not detected in 286 (38%). In the group without detectable embryonic cardiac activity, the breakdown of crown-rump lengths was as follows: 100 measuring less than 5 mm; 36 measuring 5 to 7 mm, and 150 measuring 7 mm or greater. The breakdown of mean sac diameters in those without a visible embryo but a visible sac was as follows: 120 measuring less than 16 mm, 90 measuring 16 to 25 mm, and 51 measuring 25 mm or greater. The 100 patients with crown-rump lengths measuring less than 5 mm without detectable embryonic cardiac activity and the 120 patients with mean sac diameters measuring less than 16 mm without a visible embryo would have required follow-up based on the old criteria and, therefore, were not included in our further computations. The application of the new extended size criteria recommended by Society of Radiologists in Ultrasound to this cohort would have resulted in follow-up sonograms in 126 (36 + 90) of the 1013 patients (12%; ie, those patients
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Hu et al—New Early First-Trimester Diagnostic Criteria for Nonviable Pregnancy
who fell between the previous criteria for pregnancy failure and the newer criteria: crown-rump length, 5–7 mm; mean sac diameter, 16–25 mm).
Discussion The stated goal of the new early first-trimester diagnostic criteria for nonviable pregnancy11 was to definitively diagnose failed pregnancy only in those cases in which the chance of a normal intrauterine gestation given the sonographic findings is virtually zero, with specificity and a positive predictive value as near to 100% as possible. To achieve this purpose, a mean sac diameter cutoff of 25 mm for empty sacs and a crown-rump length cutoff of 7 mm for embryos without a heartbeat were introduced to replace prior, less stringent criteria and, thus, to more definitively diagnose a failed pregnancy and, to the greatest degree possible, exclude possible inadvertent interruption of a viable pregnancy. However, introduction of these more stringent criteria will necessarily result in an increased number of follow-up sonographic examinations, thus incurring additional medical costs and, perhaps more importantly, furthering maternal uncertainty and anxiety regarding the status of the pregnancy. Of course, we are not equating the financial impact with the more important goal of limiting erroneous interruptions of potentially viable pregnancies to an absolute minimum.
It was not our intention to investigate the outcomes or to determine a final absolute value that invariably signifies an early failed pregnancy. Our study was designed to find out how many additional follow-up sonograms are potentially required by determining the number of sonograms falling into the zones altered by the new, more stringent criteria of crown-rump length of 5 to 7 mm without a heartbeat, and mean sac diameter of 16 to 25 mm without a visible embryo. To our knowledge, this work was the first study performed to evaluate the impact of the new size criteria. Although our study was retrospective, we do not believe this factor to be an important weakness because of the large study cohort. Although it would be preferable that a prospective study ultimately confirms our results, we are confident that such a study would confirm our findings. We found that of 1013 patients examined for threatened abortion, 126 (12%) fell into these crown-rump length and mean sac diameter ranges. Even among those diagnosticians who adopt the more stringent criteria (crown-rump length, 7 mm; mean sac diameter, 25 mm), an additional examination would be recommended in fewer than 1 per 8 patients. Therefore, we conclude that these changes affect a relatively small number of patients and do minimize critical errors and potential harm to a normal intrauterine gestation, a much more important change than the resulting additional medical tests for some patients.
References Figure 1. Total 1013 sonograms in 10 years (1999–2008) included in the study. Total number of patients who fell into the gray zones (crown-rump length, 5–7 mm; mean sac diameter [MSD], 16–25 mm): 36 + 90 = 126 of 1013 (12%).
1.
2.
3.
4.
5.
6.
J Ultrasound Med 2014; 33:1585–1588
Laing FC, Frates MC, Benson CB. Ultrasound evaluation during the first trimester of pregnancy. In: Callen PW (ed). Ultrasonography in Obstetrics and Gynecology. 5th ed. Philadelphia, PA: WB Saunders Co; 2007:181– 224. Aziz S, Cho RC, Baker DB, Chhor C, Filly RA. “Empty” sac in pregnant women with bleeding: are measurements answering the right question? J Clin Ultrasound 2009; 37:249–252. Aziz S, Cho RC, Baker DB, Chhor C, Filly RA. Five-millimeter and smaller embryos without embryonic cardiac activity: outcomes in women with vaginal bleeding. J Ultrasound Med 2008; 27:1559–1561. Levi CS, Lyons EA, Zheng XH, Lindsay DJ, Holt SC. Endovaginal US: demonstration of cardiac activity in embryos of less than 5.0 mm in crownrump length. Radiology 1990; 176:71–74. Brown DL, Emerson DS, Felker RE, Cartier MS, Smith WC. Diagnosis of embryonic demise by endovaginal sonography. J Ultrasound Med 1990; 9:631–636. Pennell RG, Needleman L, Pajak T, et al. Prospective comparison of vaginal and abdominal sonography in normal early pregnancy. J Ultrasound Med 1991; 10:63–67.
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7.
Abdallah Y, Daemen A, Kirk E, et al. Limitations of current definitions of miscarriage using mean gestational sac diameter and crown-rump length measurements: a multicenter observational study. Ultrasound Obstet Gynecol 2011; 38:497–502. 8. Doubilet PM, Benson CB. First, do no harm . . . to early pregnancies. J Ultrasound Med 2010; 29:685–689. 9. Jeve Y, Rana R, Bhide A, Thangaratinam S. Accuracy of first-trimester ultrasound in the diagnosis of early embryonic demise: a systematic review. Ultrasound Obstet Gynecol 2011; 38:489–496. 10. Pexsters A, Luts J, van Schoubroeck D, et al. Clinical implications of intraand interobserver reproducibility of transvaginal sonographic measurement of gestational sac and crown-rump length at 6–9 weeks’ gestation. Ultrasound Obstet Gynecol 2011; 38:510–515. 11. Doubilet PM, Benson CB, Bourne T, et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med 2013; 369:1443– 1451.
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ORIGINAL RESEARCH
Impact of New Society of Radiologists in Ultrasound Early First-Trimester Diagnostic Criteria for Nonviable Pregnancy Maowen Hu, MD, Liina Poder, MD, Roy A. Filly, MD
Objectives—New early first-trimester diagnostic criteria for nonviable pregnancy recommended by the Society of Radiologists in Ultrasound via a multispecialty consensus panel extended the diagnostic size criteria of crown-rump length from 5 to 7 mm for embryos without a heartbeat and mean sac diameter from 16 to 25 mm for “empty” sacs. Our study assessed the potential impact of the new criteria on the number of additional follow-up sonograms these changes would engender. Methods—A retrospective study of all first-trimester sonograms in women with first trimester bleeding from 1999 to 2008 was conducted. Everyone included in the study had a visible gestational sac in the uterus. There were no pregnancies of unknown location or ectopic pregnancies included in this study cohort. Pregnancy of unknown location was used to describe cases in which there were no signs of pregnancy inside or outside the uterus on transvaginal sonography despite a positive pregnancy test result. A total of 1013 patients met the inclusion criteria. Results—Seven hundred fifty-two patients (74%) had identifiable embryos, and 261 (26%) did not. Of those with an identifiable embryo, 286 (38%) had no detectable embryonic cardiac activity. The breakdown of crown-rump lengths in this group was as follows: 100 measuring less than 5 mm, 36 measuring 5 to 7 mm, and 150 measuring 7 mm or greater. The breakdown of mean sac diameters in those without a visible embryo was as follows: 120 measuring less than 16 mm, 90 measuring 16 to 25 mm, and 51 measuring 25 mm or greater. Conclusions—When diagnosing a failed pregnancy, there can be no room for error. Only 126 of 1013 early pregnancies threatening to abort (12%) fell into the more conservative zones defined by the new compared to the former size criteria (crown-rump length, 5–7 mm; mean sac diameter, 16–25 mm). Therefore, the potential impact of the new guidelines on follow-up sonograms does not appear inordinate. Key Words—bleeding; embryo; nonviable; obstetric ultrasound; sonography; threatened abortion; ultrasound education Received November 28, 2013, from the from the Department of Radiology, University of California, San Francisco, California USA. Revision requested December 9, 2013. Revised manuscript accepted for publication December 28, 2013. Address correspondence to Liina Poder, MD, Department of Radiology, University of California, 505 Parnassus Ave, PO Box 0628, San Francisco, CA 94143-0628 USA. E-mail: [email protected] doi:10.7863/ultra.33.9.1585
S
onography plays a pivotal role in the evaluation of women who are bleeding in the first trimester of pregnancy. A variety of sonographic features have been studied in the literature for trying to identify early pregnancy failure.1–3 The criteria most often used to diagnose pregnancy failure include absence of cardiac activity by a certain crown-rump length and no visible embryo by a certain mean gestational sac diameter. However, there are variations in cutoff values for mean sac diameter and crown-rump length used to define pregnancy failure by different observers and approved by
©2014 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2014; 33:1585–1588 | 0278-4297 | www.aium.org
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Hu et al—New Early First-Trimester Diagnostic Criteria for Nonviable Pregnancy
different organizations (most notably the American College of Radiology and the Royal College of Obstetricians and Gynaecologists). In the most common criteria used in the United States, no follow-up sonogram was recommended for patients showing an embryo with a crownrump length of 5 mm or greater and no heartbeat or for gestational sacs measuring 16 mm or greater in mean sac diameter and lacking an embryo.4–6 However, a recent meta-analysis of previous data showed that there is a substantial likelihood that 5-mm crown-rump length and 16-mm mean sac diameter cutoffs result in false-positive diagnoses, which place normal intrauterine pregnancies at risk for inappropriate termination.7 Recent studies involving many more patients also reported several cases of embryos with a crown-rump length of 5 to 6 mm and no heartbeat or a mean sac diameter of 17 to 21 mm (interobserver variability, 17–25 mm) and no visible embryo that subsequently proved to be viable pregnancies.7–10 Incorrect diagnosis of pregnancy failure can prompt interventions that interrupt a pregnancy that otherwise would have had a normal outcome. To minimize or avoid false-positive test results, more stringent diagnostic criteria for nonviability by expanding the crown-rump length cutoff to 7 mm for embryos without a heartbeat and the mean sac diameter cutoff to 25 mm for “empty” sacs was recently recommended by a Society of Radiologists in Ultrasound multispecialty consensus panel.11 Although these more conservative new criteria will potentially lead to a diminishingly small number of false-positive diagnoses of nonviable pregnancy, they also raise the question of the effect they will have on increasing the number of followup sonograms. Our study was designed to address the latter issue.
Materials and Methods A retrospective review of all sonograms from women who had bleeding or “spotting” in the first trimester and were scanned at the University of California San Francisco Medical Center in the 10 years from 1999 to 2008 was undertaken. A total of 1028 initial sonographic examinations were performed during this period. Follow-up examinations were excluded. However, the initial sonograms of different pregnancies in the same woman were included. Of these 1028 initial examinations, 15 of the sonograms were irretrievable at the time of the review and were excluded. Therefore, a total of 1013 sonograms were included in this study. Everyone included in the study had a visible gestational sac in the uterus. There were no pregnancies of unknown location or ectopic pregnancies included in this
1586
study cohort. Pregnancy of unknown location was used to describe cases in which there were no signs of pregnancy inside or outside the uterus on transvaginal sonography despite a positive pregnancy test result. Each patient was scanned with both transabdominal and endovaginal techniques (Acuson Sequoia; Siemens Medical Solutions, Mountain View, CA) by a sonographer according to the University of California San Francisco protocol. Transabdominal transducers used included vector arrays with selectable frequencies ranging from 1 to 4 MHz and curved arrays with selectable frequencies ranging from 2 to 6 MHz. The endovaginal transducer used was a tightly curved array with selectable frequencies from 4 to 8 MHz. The reports of these sonograms were reviewed for the presence or absence of an embryo/fetus, presence or absence of a heartbeat if an embryo/fetus was observed, and mean sac diameter if no embryo/fetus was observed. If an embryo was seen, then the crown-rump length was measured in millimeters to the nearest 10th of a millimeter. The mean sac diameter was measured in millimeters, again to the nearest 10th of a millimeter. Follow-up was not undertaken to determine the outcomes of these pregnancies. The University of California San Francisco Committee on Human Research approved this study.
Results Of the 1013 first-trimester sonograms obtained from women with bleeding or spotting in the first trimester, 752 (74%) showed an identifiable embryo, and 261 (26%) had no identifiable embryo within the visible gestational sac (Figure 1). Of those with an identifiable embryo, embryonic cardiac activity was detected in 466 (62%) and not detected in 286 (38%). In the group without detectable embryonic cardiac activity, the breakdown of crown-rump lengths was as follows: 100 measuring less than 5 mm; 36 measuring 5 to 7 mm, and 150 measuring 7 mm or greater. The breakdown of mean sac diameters in those without a visible embryo but a visible sac was as follows: 120 measuring less than 16 mm, 90 measuring 16 to 25 mm, and 51 measuring 25 mm or greater. The 100 patients with crown-rump lengths measuring less than 5 mm without detectable embryonic cardiac activity and the 120 patients with mean sac diameters measuring less than 16 mm without a visible embryo would have required follow-up based on the old criteria and, therefore, were not included in our further computations. The application of the new extended size criteria recommended by Society of Radiologists in Ultrasound to this cohort would have resulted in follow-up sonograms in 126 (36 + 90) of the 1013 patients (12%; ie, those patients
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who fell between the previous criteria for pregnancy failure and the newer criteria: crown-rump length, 5–7 mm; mean sac diameter, 16–25 mm).
Discussion The stated goal of the new early first-trimester diagnostic criteria for nonviable pregnancy11 was to definitively diagnose failed pregnancy only in those cases in which the chance of a normal intrauterine gestation given the sonographic findings is virtually zero, with specificity and a positive predictive value as near to 100% as possible. To achieve this purpose, a mean sac diameter cutoff of 25 mm for empty sacs and a crown-rump length cutoff of 7 mm for embryos without a heartbeat were introduced to replace prior, less stringent criteria and, thus, to more definitively diagnose a failed pregnancy and, to the greatest degree possible, exclude possible inadvertent interruption of a viable pregnancy. However, introduction of these more stringent criteria will necessarily result in an increased number of follow-up sonographic examinations, thus incurring additional medical costs and, perhaps more importantly, furthering maternal uncertainty and anxiety regarding the status of the pregnancy. Of course, we are not equating the financial impact with the more important goal of limiting erroneous interruptions of potentially viable pregnancies to an absolute minimum.
It was not our intention to investigate the outcomes or to determine a final absolute value that invariably signifies an early failed pregnancy. Our study was designed to find out how many additional follow-up sonograms are potentially required by determining the number of sonograms falling into the zones altered by the new, more stringent criteria of crown-rump length of 5 to 7 mm without a heartbeat, and mean sac diameter of 16 to 25 mm without a visible embryo. To our knowledge, this work was the first study performed to evaluate the impact of the new size criteria. Although our study was retrospective, we do not believe this factor to be an important weakness because of the large study cohort. Although it would be preferable that a prospective study ultimately confirms our results, we are confident that such a study would confirm our findings. We found that of 1013 patients examined for threatened abortion, 126 (12%) fell into these crown-rump length and mean sac diameter ranges. Even among those diagnosticians who adopt the more stringent criteria (crown-rump length, 7 mm; mean sac diameter, 25 mm), an additional examination would be recommended in fewer than 1 per 8 patients. Therefore, we conclude that these changes affect a relatively small number of patients and do minimize critical errors and potential harm to a normal intrauterine gestation, a much more important change than the resulting additional medical tests for some patients.
References Figure 1. Total 1013 sonograms in 10 years (1999–2008) included in the study. Total number of patients who fell into the gray zones (crown-rump length, 5–7 mm; mean sac diameter [MSD], 16–25 mm): 36 + 90 = 126 of 1013 (12%).
1.
2.
3.
4.
5.
6.
J Ultrasound Med 2014; 33:1585–1588
Laing FC, Frates MC, Benson CB. Ultrasound evaluation during the first trimester of pregnancy. In: Callen PW (ed). Ultrasonography in Obstetrics and Gynecology. 5th ed. Philadelphia, PA: WB Saunders Co; 2007:181– 224. Aziz S, Cho RC, Baker DB, Chhor C, Filly RA. “Empty” sac in pregnant women with bleeding: are measurements answering the right question? J Clin Ultrasound 2009; 37:249–252. Aziz S, Cho RC, Baker DB, Chhor C, Filly RA. Five-millimeter and smaller embryos without embryonic cardiac activity: outcomes in women with vaginal bleeding. J Ultrasound Med 2008; 27:1559–1561. Levi CS, Lyons EA, Zheng XH, Lindsay DJ, Holt SC. Endovaginal US: demonstration of cardiac activity in embryos of less than 5.0 mm in crownrump length. Radiology 1990; 176:71–74. Brown DL, Emerson DS, Felker RE, Cartier MS, Smith WC. Diagnosis of embryonic demise by endovaginal sonography. J Ultrasound Med 1990; 9:631–636. Pennell RG, Needleman L, Pajak T, et al. Prospective comparison of vaginal and abdominal sonography in normal early pregnancy. J Ultrasound Med 1991; 10:63–67.
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7.
Abdallah Y, Daemen A, Kirk E, et al. Limitations of current definitions of miscarriage using mean gestational sac diameter and crown-rump length measurements: a multicenter observational study. Ultrasound Obstet Gynecol 2011; 38:497–502. 8. Doubilet PM, Benson CB. First, do no harm . . . to early pregnancies. J Ultrasound Med 2010; 29:685–689. 9. Jeve Y, Rana R, Bhide A, Thangaratinam S. Accuracy of first-trimester ultrasound in the diagnosis of early embryonic demise: a systematic review. Ultrasound Obstet Gynecol 2011; 38:489–496. 10. Pexsters A, Luts J, van Schoubroeck D, et al. Clinical implications of intraand interobserver reproducibility of transvaginal sonographic measurement of gestational sac and crown-rump length at 6–9 weeks’ gestation. Ultrasound Obstet Gynecol 2011; 38:510–515. 11. Doubilet PM, Benson CB, Bourne T, et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med 2013; 369:1443– 1451.
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