OBJECTIVE: To present prenatal diagnosis and molecular cytogenetic 
characterization of a de novo 5q35 microdeletion associated with Sotos syndrome.
METHODS: This was the first pregnancy of a 29-year-old woman. The pregnancy was 
uneventful until 27 weeks of gestation when left ventriculomegaly was first 
noted. At 31 weeks of gestation, polyhydramnios, macrocephaly, and 
ventriculomegaly were prominent on ultrasound, and left pyelectasis and 
bilateral ventriculomegaly were diagnosed on magnetic resonance imaging. The 
woman underwent amniocentesis and cordocentesis at 32 weeks of gestation. 
Conventional cytogenetic analysis was performed using cultured amniocytes and 
cord blood lymphocytes. Array comparative genomic hybridization (aCGH) was 
performed on uncultured amniocytes and parental blood. Metaphase fluorescence in 
situ hybridization (FISH) was performed on cultured lymphocytes.
RESULTS: Conventional cytogenetics revealed a karyotype of 46,XX. aCGH on 
uncultured amniocytes revealed a de novo 1.07-Mb microdeletion at 5q35.2-q35.3 
encompassing NSD1. Metaphase FISH analysis on the cord blood lymphocytes 
confirmed the deletion at 5q35.2. The postnatal phenotype was consistent with 
Sotos syndrome.
CONCLUSION: Fetuses with Sotos syndrome may present macrocephaly, 
polyhydramnios, ventriculomegaly, and pyelectasis in the third trimester. aCGH 
and metaphase FISH are useful for rapid diagnosis of 5q35 microdeletion 
associated with Sotos syndrome.