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Colorado Genetics Laboratory

Percutaneous Umbilical Blood Sample Chromosome Analysis


Percutaneous umbilical blood sample (PUBS) cytogenetic analysis is performed to detect abnormal chromosome number and structural rearrangements, such as:

    • Trisomies
    • Monosomies
    • Larger interstitial or terminal deletions and duplications
    • Translocations
    • Inversions
    • Mosaicism

Chromosome analysis on PUBS is ordered when:

    • Fetal abnormalities are observed on ultrasound
    • Amniotic fluid or CVS sample cannot be obtained, such as when severe oligohydramnios is present

Trisomy screen by FISH for trisomies 21, 13, 18 and sex chromosome aneuploidies using fluorescence in situ hybridization (FISH) is commonly performed in conjunction with PUBS chromosome analysis.


A minimum of 20 metaphases are examined and 2 karyotypes prepared from cultured preparations.

Specimen Requirements
    • Obtain 1-2 ml percutaneous umbilical blood in a 3 cc sodium heparin, green top tube or sodium heparin rinsed syringe
    • Label specimen tube with patient’s name and a second identifier (ex: DOB, hospital ID)
    • Maintain specimen at room temperature and transport to the Colorado Genetics Laboratory immediately


Complete a Test Request Form​​​. Indicate test requested in the “Prenatal/Tissue Specimens” section of the form, and include pertinent clinical information and gestational age at the time of specimen collection.​