Clinical Significance of Non-Invasive Prenatal Screening for Trisomy 7: Cohort Study and Literature Review

• Published in: Genes 2020-12, Vol.12 (1), p.11
• Main Authors: Zhu, Xiaofan, Lam, Doris Yuk Man, Chau, Matthew Hoi Kin, Xue, Shuwen, Dai, Peng, Zhao, Ganye, Cao, Ye, Cheung, Sunny Wai Hung, Kwok, Yvonne Ka Yin, Choy, Kwong Wai, Kong, Xiangdong, Leung, Tak Yeung
• Format: Article
• Language: English
• ISSN: 2073-4425; 2073-4425
• DOI: 10.3390/genes12010011

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.