Clinical manifestations and the prenatal diagnosis of trisomy 7 mosaicism: Two case reports

Abstract

Background: The clinical manifestations of trisomy 7 mosaicism are diverse and nonspecific, so prenatal diagnosis is very difficult.

Case summary: Two pregnant women with abnormal prenatal screening results were included. One was a 22-year-old woman (G1P0). At 31^st week of gestation, ultrasound revealed that the posterior horn of the left lateral ventricle was 10 mm and the right renal pelvis had a separation of 7 mm. The other pregnant woman was 33 years old (G2P1L1A0), and her fetus was found to have a cardiac malformation at the 24^th week of gestation. Copy number variation sequencing, whole-exome sequencing and karyotype analysis were carried out after amniocentesis, and both fetuses were diagnosed with trisomy 7 mosaicism. After parental counseling, one woman continued the pregnancy, and the other woman terminated the pregnancy.

Conclusion: In trisomy 7 mosaicism, the low proportion of trisomy does not lead to abortion, but can result in abnormal fetal development, which can be detected via ultrasound. Therefore, clinicians need to pay more attention to various aspects of fetal growth and development, combining with imaging, cellular, molecular genetics and other methods to perform comprehensive evaluations of fetuses to provide more reliable genetic counseling for pregnant women.

Keywords: Case report; Copy number variation sequencing; Karyotype analysis; Prenatal diagnosis; Trisomy 7 mosaicism; Whole-exome sequencing.