Prenatal diagnosis of de novo monosomy 18p deletion syndrome by chromosome microarray analysis: Three case reports.

Rationale: Monosomy 18p deletion syndrome refers to a rare chromosomal disorder resulting from the part deletion of the short arm of chromosome 18. Prenatal diagnosis of de novo 18p deletion syndrome is a challenge due to its low incidence and untypical prenatal clinical presentation. Patient concerns: Three cases received amniocentesis due to increased nuchal translucency (INT), high risk for Down syndrome, and INT combined intrauterine growth retardation (IUGR), respectively. Diagnosis: The 3 cases were diagnosed with de novo monosomy 18p deletion syndrome by amniocentesis and chromosome microarray analysis (CMA). Interventions: Karyotype analysis and CMA were used to analyze the abnormal chromosome. Outcomes: Case 1 and case 2 revealed 13.87 and 12.68 Mb deletions by array-CGH analysis, respectively. Case 3 revealed 6.9 Mb deletions in 18p11.32p11.31 and 7.5 Mb deletions in 18p11.23p11.21 by SNP array. All of the pregnancies were terminated due to the abnormal chromosome. Lessons: The fetal phenotype of monosomy 18p deletion syndrome shows great variability and may not be evident during the pregnancy. CMA may be served as an effective tool for the diagnosis of prenatal monosomy 18p deletion syndrome diagnosis.