Trisomy 7 is the most frequently observed type of rare autosomal trisomies in genome-wide non-invasive prenatal screening (NIPS). Currently, the clinical significance of trisomy 7 NIPS-positive results is still unknown. We reviewed two independent cohorts from two laboratories where similar NIPS metrics were applied. A total of 70,441 singleton cases who underwent genome-wide NIPS were analyzed, among which 39 pregnancies were positive for trisomy 7, yielding a screen-positive rate of 0.055% (39/70,441). There were 28 cases with invasive testing results available; the positive predictive value (PPV) was 3.6% (1/28). We then searched the published NIPS studies to generate a large cohort of 437,873 pregnancies and identified 247 cases (0.056%) that were screened positive for trisomy 7. The overall PPV was 3.4% (4/118) in the combined data. The presence of uniparental disomy 7 was not detected in the NIPS trisomy 7-positive pregnancies with normal fetal karyotype. Among the 85 cases with pregnancy outcome available in combined data, 88.2% were normal live births, 14.1% had intrauterine growth restriction, preterm birth or low birth weight, 3.5% presented with ultrasound abnormality, and no fetal loss was observed. Our data provide valuable information for counseling and management of trisomy 7-positive NIPS pregnancies.
ObjectiveTo report genome‐wide cell‐free DNA (cfDNA) screening facilitating the diagnosis of Pallister‐Killian syndrome (PKS).MethodsThis is a retrospective cohort analysis of positive genome‐wide cfDNA screening results showing increased signal from chromosome 12 and the detection of PKS. The genome‐wide cfDNA screening results and the subsequent investigations were reviewed.ResultsThree singleton pregnancies (3/29007) from 2016 to 2017 yielded positive results indicating large gains on the entire p‐arm of chromosome 12. In two cases, multiple structural abnormalities were detected by prenatal ultrasound and the couples opted for termination of pregnancy. Chromosomal microarray performed on fetal skin tissues of the two abortuses detected mosaic tetrasomy 12p, consistent with PKS. In the third case, karyotype and chromosomal microarray performed on an amniotic fluid sample also showed mosaic tetrasomy 12p. In each of the three cases, genome‐wide cfDNA screening revealed a large gain on chromosome 12p; subsequent prenatal or postnatal diagnostic testing confirmed the diagnosis of PKS.ConclusionWe report the ability of genome‐wide cfDNA screening to provide early suspicion and facilitate the subsequent genetic diagnosis of PKS. As genome‐wide cfDNA screening becomes increasingly available, incidental diagnosis of partial aneuploidies is expected to increase.
Virtual poster abstractsthe parents about the expected health problems can be given and vice versa inconspicuous results decrease the risk for an underlying genetic disease. This valuable Information can help the parents to make an informed and safer decision about the continuation of pregnancy.
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