Fetal nuchal translucency in early detection of Down´s syndrome

A more recent review of the literature is reported in Methods of Early Prenatal Diagnosis, SBU report 182, published 2006.

Findings by SBU Alert

Version: 1

Technology and target group

A relatively new method for assessing the risk for chromosomal abnormalities in the fetus, particularly Down´s syndrome, involves the use of ultrasound to measure subcutaneous fluid accumulation behind the neck (fetal nuchal translucency). The test can be performed in gestational weeks 10 to 14. The calculated risk for Down´s syndrome in a fetus is based on the nuchal translucency measurement, maternal age, and gestational age. Fetal nuchal translucency screening can also be combined with a blood test for maternal serum analysis. Mothers at high risk are offered an invasive procedure, ie, amniocentesis or chorionic villus sampling, to establish a diagnosis. The target group for fetal nuchal translucency may vary from the usual target group for amniocentesis or chorionic villus sampling (mainly women aged 35 years and older) to all pregnant women.

Patient benefits

No controlled studies have compared this method with the current standard practice, ie, risk assessment based only on maternal age. Open studies and model studies of the method that include all pregnant women have resulted in the detection of a higher percentage of fetuses with Down´s syndrome. Concurrently, fewer amniocentesis procedures are required per detected case, resulting in a lower number of amniocentesis-induced miscarriages per detected case. 

Ethical aspects

All fetal diagnostic tests are associated with short-term and long-term ethical dilemmas for the individual and society. The decision to use these examinations must be based on the expectant parents wishes. Hence, it is important that parents receive accurate and understandable information about the expected consequences of the different examinations. Expectant parents should be made aware that the tests might also detect other abnormalities in the fetus. 

Scientific evidence

There is moderate* scientific documentation on the methods capacity to assess the risk for Down´s syndrome in a fetus. No* scientific documentation is available on the costs and cost-effectiveness of the method.

Much of the documentation suggests that several new methods or combinations of methods have certain advantages compared to the current standard practice. However, knowledge on the relative effectiveness of the different strategies is limited, and this area needs further study. Hence, the use of fetal nuchal translucency to assess the risk for Down´s syndrome should take place only within the framework of scientific studies that encompass research on the acceptance of the method, the characteristics of the method in broad application, and its ethical, psychological, and economic consequences. It is essential to complete the ongoing controlled trials prior to general dissemination of the method in healthcare.

*This assessment by SBU Alert uses a 4-point scale to grade the quality and evidence of the scientific documentation. The grades indicate: (1) good, (2) moderate, (3) poor, or (4) no scientific evidence on the subject.

This summary is based on a report prepared at SBU in collaboration with Sissel Saltvedt, MD, Danderyds Sjukhus, and has been reviewed by The-Hung Bui, MD PhD, The Karolinska Hospital.

The full report is available only in Swedish.

Alert is a joint effort by the Swedish Council on Technology Assessment in Health Care (SBU), the Medical Products Agency, the National Board of Health and Welfare, and the Federation of Swedish County Councils.

References

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