DESCRIPTION
Definitive diagnosis of Down syndrome and other chromosomal abnormalities requires amniocentesis or chorionic villus sampling (CVS), both of which are invasive procedures with associated risk to the pregnancy. Less invasive screening programs have been developed with the use of biochemical markers that show an association with Down syndrome.
There has also been interest in ultrasound markers to improve the accuracy of biochemical screening. One potential marker is fetal nuchal translucency. This refers to the ultrasound detection of subcutaneous edema in the fetal neck, found between 11 weeks 0 days and 13 weeks 6 days of gestation and is measured as the maximal thickness of the sonolucent zone between the inner aspect of the fetal skin and the outer aspect of the soft tissue overlying the cervical spine or the occipital bone. Studies have reported an association between increased nuchal translucency in the first trimester of pregnancy and chromosomal defects. Nuchal translucency can be done alone as a first-trimester screen, or in combination with the maternal serum markers, free beta subunit of human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein-A (PAPP-A).
Another potential ultrasound marker is fetal nasal bone examination. The technique for assessing the nasal bone using ultrasound involves viewing the fetal face longitudinally and exactly in the midline. The nasal bones are considered to be present if the line within the bridge of the nose is more echogenic than the overlying skin and absent if the echogenicity is the same or less than the skin, or if it is not visible. The absence of fetal nasal bone is considered to be a positive test result, indicating an increased risk of Down syndrome.
POLICY
First-trimester screening for detection of Down syndrome incorporating maternal serum markers and measurement of fetal nuchal translucency may be considered medically necessary if the medical appropriateness criteria are met. (See Medical Appropriateness below.)
First-trimester screening for detection of Down syndrome using measurement of nuchal translucency alone is investigational.
First-trimester screening for detection of Down syndrome using fetal nasal bone assessment translucency is investigational.
MEDICAL APPROPRIATENESS
First-trimester screening for detection of Down syndrome is considered medically appropriate if ALL of the following criteria are met:
Screening incorporates maternal serum markers and measurement of fetal nuchal translucency
Performed between 11 weeks 0 days and 13 weeks 6 days of gestation
Individual desires information regarding risk of Down Syndrome
Individual has been adequately counseled
IMPORTANT REMINDER
We develop Medical Policies to provide guidance to Members and Providers. This Medical Policy relates only to the services or supplies described in it. The existence of a Medical Policy is not an authorization, certification, explanation of benefits or a contract for the service (or supply) that is referenced in the Medical Policy. For a determination of the benefits that a Member is entitled to receive under his or her health plan, the Member's health plan must be reviewed. If there is a conflict between the Medical Policy and a health plan, the express terms of the health plan will govern.
ADDITIONAL INFORMATION
This policy does not address the second trimester maternal markers which measure alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol (i.e., triple screen) or the addition of a fourth marker, inhibin-A (quadruple screen).
There is insufficient evidence on the performance of fetal nasal bone assessment in average-risk populations. Several experts in the field are proposing that fetal nasal bone assessment be used as a second stage of screening, to screen women found to be of borderline risk using maternal serum markers and nuchal translucency. Additional studies using this contingent approach are needed before conclusions can be drawn about its utility.
SOURCES
BlueCross BlueShield Association. Medical Policy Reference Manual. (3:2010). First Trimester Detection of Down Syndrome Using Fetal Ultrasound Markers Combined with Maternal Serum Assessment (4.01.14). Retrieved April 7, 2011 from BlueWeb. (27 articles and/or guidelines reviewed)
Driscoll, D., & Gross, S. (2009). ACMG practice guideline: Screening for fetal aneuploidy and neural tube defects. Genetics in Medicine, 11 (11), 818-821.
Kagan, K., Etchegaray, A., Zhou, Y., Wright, D., & Nicolaides, K. (2009). Prospective validation of first trimester combined screening for trisomy 21. Ultrasound Obstetrics and Gynecology, 34 (1), 14-18. (Level 2 Evidence - Independent)
McLennan, A., Schluter, P., Pincham, V., & Hyett, J. (2009). First-trimester fetal nasal bone audit: evaluation of a novel method of image assessment. Ultrasound Obstetrics and Gynecology, 34 (6), 623-628. (Level 4 Evidence - Independent)
National Guideline Clearinghouse. American College of Obstetricians and Gynecologists (2007) Screening for fetal chromosomal abnormalities. Retrieved April 11, 2011 from http://www.guideline.gov/content.aspx?id=10921&search=acog+fetal+chromosomal.
National Institute for Health and Clinical Excellence. (2008, March). Antenatal care. Retrieved April 11, 2011 from http://www.nice.org.uk/nicemedia/live/11947/40115/40115.pdf.
Society of Obstetricians and Gynaecologists of Canada. SOGC clinical practice guideline: Prenatal screening for fetal aneuploidy. Retrieved April 11, 2011 from http://www.sogc.org/guidelines/documents/187E-CPG-February2007.pdf.
ORIGINAL EFFECTIVE DATE: 9/11/2011
MOST RECENT REVIEW DATE: 9/11/2011
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Policies included in the Medical Policy Manual are not intended to certify coverage availability. They are medical determinations about a particular technology, service, drug, etc. While a policy or technology may be medically necessary, it could be excluded in a member's benefit plan. Please check with the appropriate claims department to determine if the service in question is a covered service under a particular benefit plan. Use of the Medical Policy Manual is not intended to replace independent medical judgment for treatment of individuals. The content on this Web site is not intended to be a substitute for professional medical advice in any way. Always seek the advice of your physician or other qualified health care provider if you have questions regarding a medical condition or treatment.
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