Lab Test

Amniotic Fluid Karyotype

Karyotyping, Chromosome Analysis, Karyogram, Amnio, GAMGT, genetic, cytogenetics

Test Codes


NOTE: Current recommendations are that SNP chromosome microarray analysis should be considered prior to karyotype for any fetus with one or more ultrasound anomalies. 



Specimen Collection Criteria

Collect: With the aid of fetal ultrasound, a qualified obstetrician collects 20-30 mL of aspirated amniotic fluid which is transferred to two sterile 15.0 mL screw cap centrifuge tubes. To avoid maternal cell contamination of the amniotic fluid specimen, the first 2 mL of fluid should be discarded.

  • The tubes should be labeled with the patient name, birth date, medical record number, requesting physician, and date and time of collection.
  • A copy of the requisition must be sent with the specimen. The requisition form must contain the patient name, birth date, medical record number, requesting physician, specimen type, and date and time of collection. Please also include gestational age and tentative diagnosis.

Physician Office/Draw Specimen Preparation

Do not freeze specimen. Maintain specimens at room temperature (20-26°C or 68-78.8°F) prior to courier pickup. For delays in transport (greater than 24 hours from the time of collection), refrigerate (2-8°C or 36-46°F) the specimen. The specimen and requisition form should be placed in a sealed transport bag.

Preparation for Courier Transport

Transport: 20-30 mL amniotic fluid, at room temperature (20-26°C or 68-78.8°F) or refrigerated (2-8°C or 36-46°F). 

Rejection Criteria

  • Specimens arriving in the Laboratory 4 days or more following the original collection date.
  • Amniotic fluid specimens with less than 5 mL of fluid will be identified as suboptimal. The Laboratory will make every effort to process suboptimal specimens but cannot guarantee a final result.

Inpatient Specimen Preparation

Cytogenetics Laboratory staff will pick up amniotic fluid specimens from fetal imaging at regularly scheduled intervals. The specimen and requisition form should be placed in a sealed transport bag.

In-Lab Processing

Specimens are processed immediately upon delivery to the Cytogenetics Laboratory. Specimens with a gestational age of 19 weeks or greater or patient's with abnormal ultrasound findings may be given a priority in processing and analysis to provide a rush result.

In situ cultures are established from amniocytes and monitored by technologists daily. Cultures are grown and evaluated daily and selected for harvest at the proper stage. Metaphase cells are examined at the microscope to screen for genetic anomalies.


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 72 hours
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days. A backup culture is maintained for two weeks past sign-out of the final report.


Royal Oak Cytogenetics Laboratory


Monday – Friday, 8:00 am – 5:00 pm.
Results available within 10 days of receipt in the Laboratory.
STAT analysis must be arranged in advance with the Laboratory.

Reference Range

Normal results would be 46,XX or 46,XY with no apparent abnormalities present.

Test Methodology

High-resolution microscopic analysis of chromosomes to provide a digital image karyotype. Special stains or techniques such as C-Banding, NOR Banding, FISH, and chromosomal microarray testing may be required to further identify specific chromosomal abnormalities or variants. 


Based on completion of chromosomal analysis. Interpretation will be issued in the form of a final report.

Clinical Utility

Karyotyping (chromosome analysis) is performed on prenatal specimens to determine the presence of chromosomal abnormalities. Karyotyping is most commonly performed on patients who are determined to be of advanced maternal age at the time of delivery (age 35 and above) or when abnormalities are determined by ultrasound, or in the presence of an abnormal AFP screen. The most common abnormalities associated with these increased risks are chromosomal aneuploidy syndromes (e.g., Down Syndrome-trisomy 21, Patau Syndrome-trisomy 13, Edward Syndrome-trisomy 18, Turner Syndrome-monosomy X), all of which can be determined by chromosome analysis.

Clinical Disease

Abnormal karyotype results should be followed up with Genetic Counseling.

CPT Codes

88235, 88267, 88280, 88285.


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