Wednesday, 8 April 2015

Statistical model for live birth prevalence from 1900 - 2010 in US, and the impact of non-invasive prenatal screening

Debate about the science and ethics of prenatal testing dates from the 1970s, and is nowhere near done with recent developments in non-invasive prenatal screening, and its predicted impact on the numbers of babies being born with Down syndrome now, and predictions for the future:


Estimates of the live births, natural losses, and elective terminations with Down syndrome in the United States
Gert de Graf, Frank Buckley and Brian Skotko, American Journal of Medical Genetics, Vol 167, Issue 4, April 2015
The present and future live birth prevalence of Down syndrome (DS) is of practical importance for planning services and prioritizing research to support people living with the condition. Live birth prevalence is influenced by changes in prenatal screening technologies and policies. To predict the future impact of these changes, a model for estimating the live births of people with DS is required. In this study, we combine diverse and robust datasets with validated estimation techniques to describe the non-selective and live birth prevalence of DS in the United States from 1900–2010. Additionally, for the period 1974–2010, we estimate the impact of DS-related elective pregnancy terminations (following a prenatal diagnosis of DS) on the live births with DS ... Our results and our model provide data on the impact of elective pregnancy terminations on live births with DS and may provide a baseline from which future trends for live births with DS can be estimated.
The full text of this important paper is freely available online here.

Prenatal Testing for Down Syndrome: Understanding Two New Studies
Amy Julia Becker, Parents.com, 3rd April 2015
... Over the course of the past decade, the prenatal testing industry has advanced and shifted. New screening tests called Non-Invasive Prenatal Screening (“NIPS”) have come on the market ... a new study ... concludes that this type of testing “had higher sensitivity, a lower false positive rate, and higher positive predictive value than did standard screening.” 
Another study came out this week ... that sheds some light on the significance of the cultural context of prenatal testing. This study analyzed decades of data about prenatal testing and the prevalence of live births of babies with Down syndrome in the United States. It concluded that the rate of live births of babies with Down syndrome is approximately 30% lower than it would be without prenatal testing, because some women choose to terminate their pregnancy after discovering their baby has Down syndrome. 
But even within the United States, the termination rates vary from population to population and from region to region ... This study suggests at least two conclusions. One, the United States as a whole contains many women who choose to have babies with Down syndrome, whether by forgoing prenatal screening tests, forgoing diagnostic tests, or choosing to continue a pregnancy with a prenatal diagnosis. Two, cultural factors play a significant role in determining who decides to terminate pregnancies once trisomy 21 has been identified ...
A sick, unethical cycle: prenatal testing for Down syndrome
Mark Leach, Down Syndrome Prenatal Testing, 3rd April 2015
So many items have cropped up in the past two weeks that here is a listing of all this news about Down syndrome prenatal testing. They lead to a sad conclusion ... But, maybe we can fix it this time with the administration of NIPS if enough people demand that laboratories and practitioners follow the guidelines and respect women seeking prenatal information by ensuring they receive ALL the information.

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