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## Complete Summary

#### GUIDELINE TITLE

Screening for fetal chromosomal abnormalities.

#### BIBLIOGRAPHIC SOURCE(S)

American College of Obstetricians and Gynecologists (ACOG). Screening
for fetal chromosomal abnormalities. Washington (DC): American College
of Obstetricians and Gynecologists (ACOG); 2007 Jan. 11 p. (ACOG
practice bulletin; no. 77). \[43 references\]

#### GUIDELINE STATUS

This is the current release of the guideline.

This guideline updates a previous version: American College of
Obstetricians and Gynecologists (ACOG). Prenatal diagnosis of fetal
chromosomal abnormalities. Washington (DC): American College of
Obstetricians and Gynecologists (ACOG); 2001 May. 12 p.(ACOG practice
bulletin; no. 27).

### COMPLETE SUMMARY CONTENT

 SCOPE\
 METHODOLOGY - including Rating Scheme and Cost Analysis\
 RECOMMENDATIONS\
 EVIDENCE SUPPORTING THE RECOMMENDATIONS\
 BENEFITS/HARMS OF IMPLEMENTING THE GUIDELINE RECOMMENDATIONS\
 QUALIFYING STATEMENTS\
 IMPLEMENTATION OF THE GUIDELINE\
 INSTITUTE OF MEDICINE (IOM) NATIONAL HEALTHCARE QUALITY REPORT
CATEGORIES\
 IDENTIFYING INFORMATION AND AVAILABILITY\
 DISCLAIMER

### SCOPE

#### DISEASE/CONDITION(S)

Fetal chromosomal abnormalities including:

-   Down syndrome

-   Trisomy 18

-   Trisomy 13

-   Turner syndrome

-   Neural tube defect

-   Other significant fetal chromosome defects

#### GUIDELINE CATEGORY

Counseling\
Diagnosis\
Prevention\
Risk Assessment\
Screening

#### CLINICAL SPECIALTY

Medical Genetics\
Obstetrics and Gynecology

#### INTENDED USERS

Physicians

#### GUIDELINE OBJECTIVE(S)

-   To aid practitioners in making decisions about appropriate obstetric
    and gynecologic care

-   To present and evaluate the best available evidence for the use of
    ultrasonographic and serum markers for selected aneuploidy screening
    in pregnancy

-   To offer practical recommendations for implementing Down syndrome
    screening in practice

#### TARGET POPULATION

Pregnant women

#### INTERVENTIONS AND PRACTICES CONSIDERED

**Screening**

**Laboratory Screening**

1.  Maternal serum alpha-fetoprotein (AFP)

2.  Free or total beta-human chorionic gonadotropin (hCG)

3.  Unconjugated estriol

4.  Inhibin A

5.  Pregnancy-associated plasma protein A (PAPP-A)

**Imaging**

1.  Ultrasonography

2.  Nuchal translucency (NT) measurement

3.  Fetal echocardiogram (for Down syndrome-related anomalies)

**Diagnostic Testing**

1.  Amniocentesis

2.  Chorionic villus sampling (CVS)

**Management**

1.  Patient counseling

2.  Trimester-appropriate screening

3.  Integrated (1^st^ and 2^nd^ trimester marker) screening

4.  Stepwise sequential screening

5.  Contingent sequential screening

6.  Test interpretation

7.  Management of multifetal gestations

#### MAJOR OUTCOMES CONSIDERED

-   Risks and benefits of diagnostic procedures

-   Predictive value of ultrasound markers of aneuploidy

-   Predictive value of diagnostic tests for detection of fetal
    chromosomal abnormalities

### METHODOLOGY

#### METHODS USED TO COLLECT/SELECT EVIDENCE

Hand-searches of Published Literature (Primary Sources)\
Hand-searches of Published Literature (Secondary Sources)\
Searches of Electronic Databases

#### DESCRIPTION OF METHODS USED TO COLLECT/SELECT THE EVIDENCE

The MEDLINE database, the Cochrane Library, and American College of
Obstetricians and Gynecologists\' (ACOG\'s) own internal resources and
documents were used to conduct a literature search to locate relevant
articles published between January 1985 and September 2006. The search
was restricted to articles published in the English language. Priority
was given to articles reporting results of original research, although
review articles and commentaries also were consulted. Abstracts of
research presented at symposia and scientific conferences were not
considered adequate for inclusion in this document. Guidelines published
by organizations or institutions such as the National Institutes of
Health and the American College of Obstetricians and Gynecologists were
reviewed, and additional studies were located by reviewing
bibliographies of identified articles.

#### NUMBER OF SOURCE DOCUMENTS

Not stated

#### METHODS USED TO ASSESS THE QUALITY AND STRENGTH OF THE EVIDENCE

Weighting According to a Rating Scheme (Scheme Given)

#### RATING SCHEME FOR THE STRENGTH OF THE EVIDENCE

Studies were reviewed and evaluated for quality according to the method
outlined by the U.S. Preventive Services Task Force:

**I** Evidence obtained from at least one properly designed randomized
controlled trial.

**II-1** Evidence obtained from well-designed controlled trials without
randomization.

**II-2** Evidence obtained from well-designed cohort or case--control
analytic studies, preferably from more than one center or research
group.

**II-3** Evidence obtained from multiple time series with or without the
intervention. Dramatic results in uncontrolled experiments also could be
regarded as this type of evidence.

**III** Opinions of respected authorities, based on clinical experience,
descriptive studies, or reports of expert committees.

#### METHODS USED TO ANALYZE THE EVIDENCE

Review of Published Meta-Analyses\
Systematic Review

#### DESCRIPTION OF THE METHODS USED TO ANALYZE THE EVIDENCE

Not stated

#### METHODS USED TO FORMULATE THE RECOMMENDATIONS

Expert Consensus

#### DESCRIPTION OF METHODS USED TO FORMULATE THE RECOMMENDATIONS

Analysis of available evidence was given priority in formulating
recommendations. When reliable research was not available, expert
opinions from obstetrician-gynecologists were used. See also the
\"Rating Scheme for the Strength of Recommendations\" field regarding
Grade C recommendations.

#### RATING SCHEME FOR THE STRENGTH OF THE RECOMMENDATIONS

Based on the highest level of evidence found in the data,
recommendations are provided and graded according to the following
categories:

**Level A** --- Recommendations are based on good and consistent
scientific evidence.

**Level B** --- Recommendations are based on limited or inconsistent
scientific evidence.

**Level C** --- Recommendations are based primarily on consensus and
expert opinion.

#### COST ANALYSIS

A formal cost analysis was not performed and published cost analyses
were not reviewed.

#### METHOD OF GUIDELINE VALIDATION

Internal Peer Review

#### DESCRIPTION OF METHOD OF GUIDELINE VALIDATION

Practice Bulletins are validated by two internal clinical review panels
composed of practicing obstetrician-gynecologists generalists and
subspecialists. The final guidelines are also reviewed and approved by
the American College of Obstetricians and Gynecologists (ACOG) Executive
Board.

### RECOMMENDATIONS

#### MAJOR RECOMMENDATIONS

The grades of evidence (I-III) and levels of recommendations (A-C) are
defined at the end of \"Major Recommendations\" field.

**The following recommendation is based on good and consistent
scientific evidence (Level A)**:

-   First-trimester screening using both nuchal translucency measurement
    and biochemical markers is an effective screening test for Down
    syndrome in the general population. At the same false-positive
    rates, this screening strategy results in a higher Down syndrome
    detection rate than does the second-trimester maternal serum triple
    screen and is comparable to the quadruple screen.

-   Measurement of nuchal translucency alone is less effective for
    first-trimester screening than is the combined test (nuchal
    translucency measurement and biochemical markers).

-   Women found to have increased risk of aneuploidy with
    first-trimester screening should be offered genetic counseling and
    the option of chorionic villus sampling (CVS) or second-trimester
    amniocentesis.

-   Specific training, standardization, use of appropriate ultrasound
    equipment, and ongoing quality assessment are important to achieve
    optimal nuchal translucency measurement for Down syndrome risk
    assessment, and this procedure should be limited to centers and
    individuals meeting these criteria.

-   Neural tube defect screening should be offered in the second
    trimester to women who elect only first-trimester screening for
    aneuploidy.

**The following recommendations are based on limited or inconsistent
scientific evidence (Level B)**:

-   Screening and invasive diagnostic testing for aneuploidy should be
    available to all women who present for prenatal care before 20 weeks
    of gestation regardless of maternal age. Women should be counseled
    regarding the differences between screening and invasive diagnostic
    testing.

-   Integrated first- and second-trimester screening is more sensitive
    with lower false-positive rates than first-trimester screening
    alone.

-   Serum integrated screening is a useful option in pregnancies where
    nuchal translucency measurement is not available or cannot be
    obtained.

-   An abnormal finding on second-trimester ultrasound examination
    identifying a major congenital anomaly significantly increases the
    risk of aneuploidy and warrants further counseling and the offer of
    a diagnostic procedure.

-   Patients who have a fetal nuchal translucency measurement of 3.5 mm
    or higher in the first trimester, despite a negative aneuploidy
    screen, or normal fetal chromosomes, should be offered a targeted
    ultrasound examination, fetal echocardiogram, or both.

-   Down syndrome risk assessment in multiple gestation using first- or
    second-trimester serum analytes is less accurate than in singleton
    pregnancies.

-   First-trimester nuchal translucency screening for Down syndrome is
    feasible in twin or triplet gestation but has lower sensitivity than
    first-trimester screening in singleton pregnancies.

**The following recommendations are based primarily on consensus and
expert opinion (Level C)**:

-   After first-trimester screening, subsequent second-trimester Down
    syndrome screening is not indicated unless it is being performed as
    a component of the integrated test, stepwise sequential, or
    contingent sequential test.

-   Subtle second-trimester ultrasonographic markers should be
    interpreted in the context of a patient\'s age, history, and serum
    screening results.

**Definitions**:

**Grades of Evidence**

**I** Evidence obtained from at least one properly designed randomized
controlled trial.

**II-1** Evidence obtained from well-designed controlled trials without
randomization.

**II-2** Evidence obtained from well-designed cohort or case--control
analytic studies, preferably from more than one center or research
group.

**II-3** Evidence obtained from multiple time series with or without the
intervention. Dramatic results in uncontrolled experiments also could be
regarded as this type of evidence.

**III** Opinions of respected authorities, based on clinical experience,
descriptive studies, or reports of expert committees.

**Levels of Recommendation**

**Level A** --- Recommendations are based on good and consistent
scientific evidence.

**Level B** --- Recommendations are based on limited or inconsistent
scientific evidence.

**Level C** --- Recommendations are based primarily on consensus and
expert opinion.

#### CLINICAL ALGORITHM(S)

None provided

### EVIDENCE SUPPORTING THE RECOMMENDATIONS

#### TYPE OF EVIDENCE SUPPORTING THE RECOMMENDATIONS

The type of supporting evidence is identified and graded for each
recommendation (see \"Major Recommendations\").

### BENEFITS/HARMS OF IMPLEMENTING THE GUIDELINE RECOMMENDATIONS

#### POTENTIAL BENEFITS

Appropriate prenatal diagnosis of fetal chromosomal abnormalities

#### POTENTIAL HARMS

-   Loss of fetus from invasive diagnostic testing

-   False positive chromosomal abnormality results

### QUALIFYING STATEMENTS

#### QUALIFYING STATEMENTS

These guidelines should not be construed as dictating an exclusive
course of treatment or procedure. Variations in practice may be
warranted based on the needs of the individual patient, resources, and
limitations unique to the institution or type of practice.

### IMPLEMENTATION OF THE GUIDELINE

#### DESCRIPTION OF IMPLEMENTATION STRATEGY

An implementation strategy was not provided.

#### IMPLEMENTATION TOOLS

Audit Criteria/Indicators\
Patient Resources

For information about
[availability](#identifying-information-and-availability), see the
\"Availability of Companion Documents\" and \"Patient Resources\" fields
below.

### INSTITUTE OF MEDICINE (IOM) NATIONAL HEALTHCARE QUALITY REPORT CATEGORIES

#### IOM CARE NEED

Staying Healthy

#### IOM DOMAIN

Effectiveness\
Patient-centeredness\
Timeliness

### IDENTIFYING INFORMATION AND AVAILABILITY

#### BIBLIOGRAPHIC SOURCE(S)

American College of Obstetricians and Gynecologists (ACOG). Screening
for fetal chromosomal abnormalities. Washington (DC): American College
of Obstetricians and Gynecologists (ACOG); 2007 Jan. 11 p. (ACOG
practice bulletin; no. 77). \[43 references\]

#### ADAPTATION

Not applicable: The guideline was not adapted from another source.

#### DATE RELEASED

2001 May (revised 2007 Jan)

#### GUIDELINE DEVELOPER(S)

American College of Obstetricians and Gynecologists - Medical Specialty
Society

#### SOURCE(S) OF FUNDING

American College of Obstetricians and Gynecologists (ACOG)

#### GUIDELINE COMMITTEE

American College of Obstetricians and Gynecologists (ACOG) Committee on
Practice Bulletins-Obstetrics

American College of Obstetricians and Gynecologists (ACOG) Committee on
Genetics

Society for Maternal-Fetal Medicine Publications Committee

#### COMPOSITION OF GROUP THAT AUTHORED THE GUIDELINE

Not stated

#### FINANCIAL DISCLOSURES/CONFLICTS OF INTEREST

Not stated

#### GUIDELINE STATUS

This is the current release of the guideline.

This guideline updates a previous version: American College of
Obstetricians and Gynecologists (ACOG). Prenatal diagnosis of fetal
chromosomal abnormalities. Washington (DC): American College of
Obstetricians and Gynecologists (ACOG); 2001 May. 12 p.(ACOG practice
bulletin; no. 27).

#### GUIDELINE AVAILABILITY

Electronic copies: None available

Print copies: Available for purchase from the American College of
Obstetricians and Gynecologists (ACOG) Distribution Center, PO Box 4500,
Kearneysville, WV 25430-4500; telephone, 800-762-2264, ext. 192; e-mail:
<sales@acog.org>. The ACOG Bookstore is available online at the [ACOG
Web site](http://www.acog.org/bookstore/).

#### AVAILABILITY OF COMPANION DOCUMENTS

Proposed performance measures are included in the original guideline
document.

#### PATIENT RESOURCES

The following is available:

-   Genetic disorders. Atlanta (GA): American College of Obstetricians
    and Gynecologists (ACOG); 2005.

Electronic copies: Available from the [American College of Obstetricians
and Gynecologists (ACOG) Web
site](http://www.acog.org/publications/patient_education/bp094.cfm).

Print copies: Available for purchase from the American College of
Obstetricians and Gynecologists (ACOG) Distribution Center, PO Box 4500,
Kearneysville, WV 25430-4500; telephone, 800-762-2264, ext. 192; e-mail:
<sales@acog.org>. The ACOG Bookstore is available online at the [ACOG
Web site](http://www.acog.org/bookstore/).

Please note: This patient information is intended to provide health
professionals with information to share with their patients to help them
better understand their health and their diagnosed disorders. By
providing access to this patient information, it is not the intention of
NGC to provide specific medical advice for particular patients. Rather
we urge patients and their representatives to review this material and
then to consult with a licensed health professional for evaluation of
treatment options suitable for them as well as for diagnosis and answers
to their personal medical questions. This patient information has been
derived and prepared from a guideline for health care professionals
included on NGC by the authors or publishers of that original guideline.
The patient information is not reviewed by NGC to establish whether or
not it accurately reflects the original guideline\'s content.

#### NGC STATUS

This NGC summary was completed by ECRI on September 22, 2004. The
information was verified by the guideline developer on December 9, 2004.
This NGC summary was updated by ECRI Institute on October 8, 2007. The
updated information was verified by the guideline developer on December
3, 2007.

#### COPYRIGHT STATEMENT

This NGC summary is based on the original guideline, which is subject to
the guideline developer\'s copyright restrictions.

### DISCLAIMER

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© 1998-2008 National Guideline Clearinghouse

Date Modified: 11/3/2008