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197: Indications for invasive prenatal testing before and after implementation of non-invasive prenatal screening

      Objective

      To evaluate the differences in number, type, and indication of invasive prenatal genetic testing in a single center prior to and following the introduction of non-invasive prenatal screening (NIPS).

      Study Design

      All genetic testing procedures between January 1, 2007 and December 31, 2015 were collected from a single center. Indication for genetic testing was determined as advanced maternal age (AMA), abnormal ultrasound findings, abnormal genetic screening, history of a parental chromosomal abnormality, history of prior aneuploid pregnancy, and risk for Mendelian disorders. NIPS was introduced at the center on February 1, 2012. Procedures prior to and after this date were compared. Fisher exact test was used to compare indications for testing prior to NIPS and after NIPS.

      Results

      A total of 2066 patients had invasive genetic testing in the study period. Of these, 43 were excluded as genetic testing was incidental to procedures performed for non-genetic indications, giving a total of 2023 patients considered for analysis. While the pre-NIPS group was longer (61 months) than the post-NIPS group (46 months) the number of patients seen was similar (49,352 vs 49,016). 1415 patients had invasive testing prior to introduction of NIPS, (489 CVS, 926 amniocentesis) and 608 patients had invasive testing following introduction of NIPS, (327 CVS, 281 amniocentesis). Average procedures per month prior to NIPS decreased from 23 to 13 per month despite an increase in patient volume per month in the unit. CVS numbers remained similar (8/month vs 7/month), however amniocentesis numbers decreased (15/month vs 7/month). Procedures with the indication of AMA (p=0.0001), abnormal genetic screening (p=0.0001), and abnormal ultrasound (p=0.002) were significantly fewer after introduction of NIPS, while procedures with the indications of prior aneuploid pregnancy (p=0.2), parental chromosomal abnormality (p=0.5), and risk for single gene disorders was not significantly changed (p=0.4).

      Conclusion

      The introduction of NIPS into clinical practice significantly lowered the number of invasive genetic tests at this single center, with decreases in amniocentesis but not CVS. Indications were significantly different, with fewer for advanced maternal age, ultrasound abnormality, and abnormal genetic screening.
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