Purpose:To determine whether maternal plasma cell–free DNA sequencing can effectively
identify trisomy 18 and 13.Methods:Sixty-two pregnancies with trisomy 18 and 12 with trisomy 13 were selected from a
cohort of 4,664 pregnancies along with matched euploid controls (including 212
additional Down syndrome and matched controls already reported), and their samples
tested using a laboratory-developed, next-generation sequencing test. Interpretation of
the results for chromosome 18 and 13 included adjustment for CG content bias.Results:Among the 99.1% of samples interpreted (1,971/1,988), observed trisomy 18 and 13
detection rates were 100% (59/59) and 91.7% (11/12) at false-positive rates of 0.28% and
0.97%, respectively. Among the 17 samples without an interpretation, three were trisomy
18. If z-score cutoffs for trisomy 18 and 13 were raised slightly, the overall
false-positive rates for the three aneuploidies could be as low as 0.1% (2/1,688) at an
overall detection rate of 98.9% (280/283) for common aneuploidies. An independent
academic laboratory confirmed performance in a subset.Conclusion:Among high-risk pregnancies, sequencing circulating cell–free DNA detects nearly
all cases of Down syndrome, trisomy 18, and trisomy 13, at a low false-positive rate.
This can potentially reduce invasive diagnostic procedures and related fetal losses by
95%. Evidence supports clinical testing for these aneuploidies.
Measurement of urine cotinine levels provides further evidence of an association between exposure to environmental tobacco smoke and pulmonary morbidity in children with asthma. These data emphasize the need for systematic, persistent efforts to stop the exposure of children with asthma to environmental tobacco smoke.
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