For a study, researchers sought to determine the effect of maternal age on the rate of clinically significant chromosomal microarray analysis results in pregnancies with abnormal maternal serum screening, as well as to determine the residual risk for abnormal microarray findings after excluding noninvasive prenatal testing (NIPT)–detectable aberrations in pregnancies with abnormal maternal serum screening.
Over the years 2013–2021, all chromosomal microarray analysis tests are done in pregnancies with abnormal maternal blood screening and normal ultrasonogram findings were included in the retrospective investigation. The frequency of clinically relevant (pathogenic and possibly pathogenic) chromosomal microarray analysis findings was compared to a local control cohort of 7,235 fetuses with normal maternal blood screening and ultrasonogram results, stratified by maternal age. The deletion of frequent NIPT-detectable abnormalities was used to calculate residual risk for clinically significant chromosomal microarray analysis results following normal NIPT. From commencement until October 2021, a systematic evaluation of research assessing the yield of chromosomal microarray analysis in fetuses with abnormal maternal serum screening was conducted, with no time or language constraints.
There were 21 clinically significant chromosomal microarray analysis results among the 559 amniocenteses conducted owing to abnormal maternal serum screening (3.8%; 95% CI 2.4–5.7%). The residual risk for chromosomal microarray analysis aberrations after theoretically normal NIPT was estimated to be 2.0% (95% CI 1.1–3.6%) (1/50), and it was significantly higher in women under the age of 35 with abnormal maternal serum screening compared to women with low-risk pregnancies. About 6 studies covering 4,890 chromosomal microarray analysis findings in pregnancies with abnormal maternal serum screening were found in a systematic review, suggesting a 2.3% residual risk for chromosomal microarray analysis abnormalities despite theoretically normal NIPT.
Clinically relevant chromosomal microarray analysis findings could be detected in one out of every 50 pregnancies with high-risk maternal serum screening following theoretically normal NIPT, meaning that invasive testing rather than NIPT should be advised in such pregnancies.