Chromosome Analysis, Routine; Rule Out Mosaic (Amniotic Fluid)

Clinical Information

Prenatal chromosome analysis can be indicated if an abnormal NIPS result has been received during pregnancy or if ultrasound features are suspicious of aneuploidy and/or mosaicism. Prenatal chromosome analysis may also be considered to evaluate for structural rearrangements (ex. translocations or inversions) or to further clarify a prenatal microarray or whole genome result.

Technical Information

For rule out mosaic chromosome analysis, 50 cells are counted to determine the modal number and a minimum of 5 cells are analyzed for chromosomal abnormalities from G-banded preparations.

Specimen Requirements

• This test can be performed on direct amniotic fluid or on cultured amniocytes.
• If sending direct fluid for microarray only, 10-20 ml of amniotic fluid is requested. Chromosomes and FISH will require an additional 10-15 ml of fluid.
• If sending cultured flasks, 2x T25 confluent flasks are required.

 

• A maternal sample is recommended to accompany the prenatal specimen for maternal cell contamination (MCC) studies. The preferred maternal sample  type for MCC is 3-4ml of peripheral blood collected in an EDTA (purple top) tube. Additional accepted maternal sample types include extracted DNA or saliva. Blood and saliva kits are available by request.
• Send approximately 5µg of extracted DNA at a requested concentration of 90-130 ng/µl.
• Saliva samples must be submitted in an approved saliva kit.

Transport Instructions

• Amniotic fluid should be kept at room temperature and should be sent by courier or overnight mail to arrive at the laboratory the next day. Do not freeze or refrigerate the specimen.
• The blood sample for MCC should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.
• Extracted DNA should be sent at room temperature via overnight delivery.
• Saliva is stable at room temperature and can be delivered via overnight or ground shipping.