ACR Guidelines for Ultrasound examination in cases of Multiple Gestations

Written by Dr. Kamal Kant Kohli Kohli Published On 2018-08-09T19:03:36+05:30 | Updated On 16 Aug 2021 4:26 PM IST

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

Dichorionic; MonochorionicMultiple gestation(s)twinsUltrasound

Source : With inputs from American College of Radiology

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Dr. Kamal Kant Kohli Kohli