ACR Guidelines for Ultrasound examination in cases of Multiple Gestations
American College of Radiology has released ACR Appropriateness Criteria for US examinations in women with multiple pregnancies which have been published in The Journal of the American College of Radiology. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. Over the past 4 decades, the increased use of assisted reproductive techniques in the United States has been associated with a substantial rise in the rate of multiple births. Women with twin or higher-order pregnancies will typically have many more US examinations than women with a singleton pregnancy.
The aim of each US varies with gestational age, and there is no accepted standard for the number of scans. However, the majority of women will have, as a minimum, a first-trimester scan, a 12-week nuchal translucency (NT) scan, a fetal anatomy scan at 18 to 22 weeks, and one or more scans in the third trimester to evaluate growth.The recommendations are based on analysis of the current medical evidence literature and the application of the RAND/UCLA appropriateness method and expert panel consensus.
Major Recommendations
- Transabdominal and transvaginal US are recommended in the first trimester when a twin pregnancy is known or suspected. Chorionicity and amnionicity are most accurately evaluated in the first trimester.
- The transabdominal US is recommended for dichorionic twins when evaluating fetal anatomy. Transvaginal US of the cervix may help triage patients into higher risk group for preterm delivery. Fetal echocardiography may be useful in some instances, such as when twins are conceived through in vitro fertilization.
- The transabdominal US is performed in monochorionic twins for fetal anatomy and to screen for fetal anomalies and TTTS. Fetal echocardiography helps screen for structural congenital cardiac anomalies. Transvaginal US of the cervix may help triage patients into higher risk group for preterm delivery. Duplex Doppler velocimetry is recommended in cases of TTTS, velamentous cord insertion, and sIUGR.
- The transabdominal US is recommended for growth and antepartum surveillance for dichorionic twins with duplex Doppler velocimetry used in cases of growth discrepancy.
- The transabdominal US is recommended for growth and antepartum surveillance for monochorionic twins. Duplex Doppler velocimetry and BPP monitoring are helpful in cases of IUGR, TTTS, TAPS, TRAP sequence, and IUFD. Fetal echocardiography should be performed to look for congenital cardiac disease and monitor cardiac function.
- Transabdominal US, duplex Doppler velocimetry, and BPP monitoring are recommended for follow-up of known twin discrepancy. Fetal echocardiography is helpful in monochorionic-monoamniotic twins.
Abbreviations
- IV, intravenous
- TTTS, twin-to-twin transfusion syndrome
- US, ultrasound
Potential adverse health effects associated with radiation exposure are an important factor to consider when selecting the appropriate imaging procedure. Because there is a wide range of radiation exposures associated with different diagnostic procedures, a relative radiation level (RRL) indication has been included for each imaging examination.
Relative Radiation Level Designations
| Relative Radiation Level* | Adult Effective Dose Estimate Range | Pediatric Effective Dose Estimate Range |
|---|---|---|
| O | 0 mSv | 0 mSv |
| <0.1 mSv | <0.03 mSv | |
| 0.1-1 mSv | 0.03-0.3 mSv | |
| 1-10 mSv | 0.3-3 mSv | |
| 10-30 mSv | 3-10 mSv | |
| 30-100 mSv | 10-30 mSv | |
| *RRL assignments for some of the examinations cannot be made, because the actual patient doses in these procedures vary as a function of a number of factors (e.g., region of the body exposed to ionizing radiation, the imaging guidance that is used). The RRLs for these examinations are designated as "Varies." | ||
ACR Appropriateness Criteria®
Multiple Gestations
Variant 1: Known or suspected multiple gestations. Monochorionic or dichorionic. First trimester US.
| Procedure | Appropriateness Category | Relative Radiation Level |
|---|---|---|
| US pregnant uterus transvaginal | Usually Appropriate | O |
| US pregnant uterus transabdominal | Usually Appropriate | O |
| US cervix transvaginal | Usually Not Appropriate | O |
| US duplex Doppler velocimetry | Usually Not Appropriate | O |
| US assessment for TTTS | Usually Not Appropriate | O |
| US pregnant uterus biophysical profile | Usually Not Appropriate | O |
| US echocardiography fetal | Usually Not Appropriate | O |
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 2: Multiple gestations. Dichorionic. Second trimester US. Anatomy scan.
| Procedure | Appropriateness Category | Relative Radiation Level |
|---|---|---|
| US pregnant uterus transabdominal | Usually Appropriate | O |
| US cervix transvaginal | Usually Appropriate | O |
| US echocardiography fetal | May Be Appropriate | O |
| US duplex Doppler velocimetry | Usually Not Appropriate | O |
| US pregnant uterus transvaginal | Usually Not Appropriate | O |
| US pregnant uterus biophysical profile | Usually Not Appropriate | O |
| US assessment for TTTS | Usually Not Appropriate | O |
Variant 3: Multiple gestations. Monochorionic. Second trimester US. Anatomy scan.
| Procedure | Appropriateness Category | Relative Radiation Level |
|---|---|---|
| US pregnant uterus transabdominal | Usually Appropriate | O |
| US assessment for TTTS | Usually Appropriate | O |
| US echocardiography fetal | Usually Appropriate | O |
| US cervix transvaginal | Usually Appropriate | O |
| US duplex Doppler velocimetry | Usually Appropriate | O |
| US pregnant uterus biophysical profile | Usually Not Appropriate | O |
| US pregnant uterus transvaginal | Usually Not Appropriate | O |
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 4: Multiple gestations. Dichorionic. Growth and antepartum surveillance.
| Procedure | Appropriateness Category | Relative Radiation Level |
|---|---|---|
| US pregnant uterus transabdominal | Usually Appropriate | O |
| US pregnant uterus biophysical profile | Usually Appropriate | O |
| US cervix transvaginal | May Be Appropriate | O |
| US duplex Doppler velocimetry | May Be Appropriate | O |
| US echocardiography fetal | Usually Not Appropriate | O |
| US pregnant uterus transvaginal | Usually Not Appropriate | O |
| US assessment for TTTS | Usually Not Appropriate | O |
Variant 5: Multiple gestations. Monochorionic. Growth and antepartum surveillance.
| Procedure | Appropriateness Category | Relative Radiation Level |
|---|---|---|
| US pregnant uterus transabdominal | Usually Appropriate | O |
| US pregnant uterus biophysical profile | Usually Appropriate | O |
| US duplex Doppler velocimetry | Usually Appropriate | O |
| US assessment for TTTS | Usually Appropriate | O |
| US echocardiography fetal | May Be Appropriate | O |
| US cervix transvaginal | May Be Appropriate | O |
| US pregnant uterus transvaginal | Usually Not Appropriate | O |
Variant 6: Multiple gestations. Known twin discordance. Monochorionic or dichorionic.
| Procedure | Appropriateness Category | Relative Radiation Level |
|---|---|---|
| US pregnant uterus transabdominal | Usually Appropriate | O |
| US duplex Doppler velocimetry | Usually Appropriate | O |
| US pregnant uterus biophysical profile | Usually Appropriate | O |
| US assessment for TTTS | Usually Appropriate | O |
| US cervix transvaginal | May Be Appropriate | O |
| US echocardiography fetal | May Be Appropriate | O |
| US pregnant uterus transvaginal | Usually Not Appropriate | O |
Benefits/Harms of Implementing the Guideline Recommendations
Potential Benefits
- For monochorionic-monoamniotic twins, recent studies have shown encouraging survival rates of greater than 90% with early diagnosis, serial ultrasound (US), and antenatal surveillance.
- Although there is no proven benefit of umbilical artery Doppler evaluation in uncomplicated twins, it has been shown to be helpful when growth delay is suspected and in monochorionic twins.
- Surveillance with a nonstress test or biophysical profile (BPP) for pregnancies complicated by abnormal fluid volumes, pregnancy-induced hypertension, fetal anomalies, growth abnormalities, monoamnionicity, or other standard obstetric indications is as reliable in multiple gestations as in singleton gestations.
- The antenatal knowledge of adverse outcome predictors such as velamentous cord insertion of vasa previa may be useful in risk stratification and management of twin pregnancies.
- A baseline cervical length assessment performed using the transvaginal US will help determine whether patients should be triaged into a higher risk group for preterm delivery.
Potential Harms
Caution is warranted in establishing the viability of a twin during early pregnancy because the demise of one of the twins is relatively common, resulting in the so-called "vanishing twin."
For Further reference log on to :
PMID: 29101986 DOI: 10.1016/j.jacr.2017.08.051
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