930 Prenatal diagnosis of single gene disorders: indication, timing, and trends

Abstract

Expanded or panethnic carrier screening for Single Gene Disorders (SGD) has increased the number of pregnancies identified as high-risk. Testing for SGD may also be performed when ultrasound (US) abnormalities are found. Our objective is to describe the circumstances of testing for SGD and to assess the impact of expanded screening. We identified pregnancies from 2015-2019 undergoing invasive testing in which testing for SGD was performed. SGD identified by carrier screening were categorized as those detectable by targeted screening, or only by expanded screening. Pregnancies in which invasive testing for SGD was performed due to carrier screening vs. US findings were compared using Fisher’s exact test, chi-square analysis, and Mann-Whitney U. Continuous data are expressed as Median [IQ Range]. A p-value <.05 was considered statistically significant. Of 1761 pregnancies undergoing invasive testing, testing for SGD was performed in 309 (17.5%). Testing was done due to carrier screening in 200 (64.7%) cases, for US findings in 86 (27.8%), and for other indications in 23 (7.4%). Preconception carrier screening was performed in most cases (53.1%). In 200 pregnancies at high-risk due to carrier screening, the most common SGD tested for were SMA (n=39), Fragile X (n=37), and CF (n=25). In 86 pregnancies at high-risk due to US, testing for Noonan Syndrome (n=64) and Skeletal Dysplasia (n=7) were most common. Invasive testing for SGD due to US findings was done at a later median gestational age, associated with higher rate of abortion, and a trend towards later median gestational age at abortion (Table 1). Between 2015 and 2019, a higher proportion of SGD identified by carrier testing could only be identified with expanded rather than targeted screening (Table 2). Though most invasive testing was performed for SGD that can be identified with targeted screening, the proportion of invasive testing for conditions detected only with expanded screening increased over time. Testing due to US findings is less common, though the majority of abortions for SGD were in this group.View Large Image Figure ViewerDownload Hi-res image Download (PPT)