Date of Award

1-1-2011

Document Type

Campus Access Thesis

Department

Genetic Counseling

First Advisor

Janice G Edwards

Abstract

Down syndrome is the most common chromosomal condition in liveborns and the most common genetic cause of intellectual disability. Two prenatal testing approaches for Down syndrome are available: screening tests and diagnostic tests. Screening tests are non-invasive but are non-diagnostic and provide an estimate of the risk of an affected pregnancy. Even with recent improvements in screening tests, definitive prenatal diagnosis can only be made by karyotyping cultured fetal cells, which must be obtained via an invasive procedure such as chorionic villus sampling (CVS) or amniocentesis.

The objective of this study was to review the published literature on termination rates among women with a prenatal diagnosis of Down syndrome in the United States. In addition, we aimed to describe temporal trends and variations with regard to maternal age, gestational age, and race/ethnicity. A systematic search of U.S. English-language articles (1995-2010) was conducted to identify primary research studies that included pregnancies with definitive prenatal diagnosis of Down syndrome and subsequent pregnancy termination rates. Studies that provided indirect estimates of pregnancy termination, such as mathematical models, were excluded. The weighted mean termination rate was calculated across studies.

Twenty-four studies were accepted. The weighted mean termination rate was 67% (range: 61%-93%) among seven population-based studies, 85% (range: 60%-90%) among nine hospital-based studies, and 50.0% (range: 0%-100%) among eight anomaly-based studies. The estimated termination rates in this review (67%-85%) are lower than those noted in previous reports (92% in Mansfield et al. (1999)). We found that termination rates decreased in recent years and also varied with maternal age, maternal race/ethnicity, and gestational age.

This systematic review presents the largest synthesis of data on termination rates following a prenatal diagnosis of Down syndrome in the United States. Importantly, a single summary termination rate may not be applicable to the entire U.S. population as it does not address regional variations and demographic differences among pregnant women across the country. In order to accurately assess the effects of changing medical and societal influences on termination rates, it is essential to collect, analyze, and publish data on patient uptake of prenatal screening, utilization of diagnostic testing, and decision-making following a definitive prenatal diagnosis of Down syndrome.

DownSyndromeEvidenceTable.xlsx (38 kB)
Down Syndrome Evidence Table (Microsoft Excel)

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