OBJECTIVE: To perform molecular cytogenetic study on two fetuses with abnormal 
ultrasound findings and analyze their genotype-phenotype correlation.
METHODS: G-banded karyotyping, single nucleotide polymorphism array (SNP array) 
and fluorescence in situ hybridization (FISH) were performed on amniotic fluid 
cells from both fetuses and peripheral blood samples from their parents. Results 
of SNP array were analyzed with bioinformatics software.
RESULTS: G-banded karyotyping failed to detect any abnormalities in both fetuses 
and their parents. SNP array detected a 2.484 Mb terminal deletion at 17p13.3 
[arr[hg19] 17p13.3 (83 035-2 567 405)×1] in fetus 1 and a 3.295 Mb terminal 
deletion at 17p13.3p13.2 [arr[hg19] 17p13.3p13.2 (83 035- 3 377 560)×1] in fetus 
2. Both deletions have overlapped with the critical region of Miller-Dieker 
syndrome (MDS) and involved candidate genes such as PAFAH1B1, YWHAE and CRK. In 
addition, SNP array and FISH analyses on the parental peripheral blood samples 
demonstrated that both 17p13.3 and 17p13.3p13.2 deletions were of de novo 
origin. Metaphase FISH performed on amniotic fluid cells confirmed the presence 
of 17p13.3 and 17p13.3p13.2 deletions detected by the SNP array, while metaphase 
FISH performed on the parents excluded any potential chromosome rearrangements.
CONCLUSION: Abnormal ultrasound features for fetuses with MDS mainly include 
central nervous system anomalies. SNP array can efficiently detect 17p13.3 
microdeletions underlying MDS, and accurately map the breakpoints and involved 
genes, which may facilitate understanding of the genotype and phenotype 
correlations for MDS.