UNASSIGNED: Nearly 9.89% of chromosome 16 consists of segmental duplications, which makes it prone to non-homologous recombination. The present study aimed to investigate the incidence and perinatal characteristics of submicroscopic chromosome 16 aberrations in prenatal diagnosis.
UNASSIGNED: A total of 2,414 consecutive fetuses that underwent prenatal chromosomal microarray analysis (CMA) between January 2016 and December 2018 were reviewed. Submicroscopic anomalies of chromosome 16 accounted for 11.1% (15/134) of all submicroscopic anomalies detected in fetuses with normal karyotype, which was larger than the percentage of anomalies in any other chromosome. The 15 submicroscopic anomalies of chromosome 16 were identified in 14 cases; 12 of them had ultrasound abnormalities. They were classified as pathogenic (N = 7), and variants of uncertain significance (N = 8). Seven fetuses with variants of uncertain significance were ended in live-born, and the remaining were end in pregnancy termination.
UNASSIGNED: Submicroscopic aberrations of chromosome 16 are frequent findings in prenatal diagnosis, which emphasize the challenge of genetic counseling and the value of CMA. Prenatal diagnosis should lead to long-term monitoring of children with such chromosomal abnormalities for better understanding of the phenotype of chromosome 16 microdeletion and microduplication syndromes.

OBJECTIVE: We present prenatal diagnosis and molecular cytogenetic characterization of a small supernumerary marker chromosome (sSMC) derived from chromosome 16.
METHODS: A 28-year-old woman underwent amniocentesis at 17 weeks of gestation because of abnormal maternal serum screening for Down syndrome. Amniocentesis revealed a karyotype of 47,XY,+mar[5]/46,XY[9]. Parental karyotypes were normal. Prenatal ultrasound findings were unremarkable. Array comparative genomic hybridization (aCGH) analysis of cultured amniocytes revealed a de novo 16% gene dosage increase of 16q11.2-q22.1. Repeat amniocentesis at 21 weeks of gestation revealed a karyotype of 47,XY,+mar[10]/46,XY[31]. aCGH analysis of uncultured amniocytes revealed a result of arr 16q11.2q22.1 (46,492,626-68,867,969) × 2.20 with a log2 ratio of 0.15 encompassing RPGRIP1L, FTO, SLC6A2, BBS2 and CDH1. Interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes detected partial trisomy 16q in 36/137 (26.3%) of uncultured amniocytes. Polymorphic DNA marker analysis on amniocytes and parental bloods excluded uniparental disomy 16. Premature labor occurred at 25 weeks of gestation, and a 585-g male baby without craniofacial dysmorphism was delivered and survived. At age 1½ years, pediatric follow-ups revealed normal psychomotor development, normal body weight, short stature, congenital hypothyroidism, hearing impairment and hypospadias in the neonate, and the peripheral blood had a karyotype of 46,XY in 40 cultured lymphocytes.
CONCLUSIONS: aCGH, interphase FISH and polymorphic DNA marker analyses of uncultured amniocytes are useful for confirmation of prenatally detected mosaic sSMCs at amniocentesis.