Express the first 1.0-2.0 mL into a separate tube to clear the specimen of possible maternal cells. Distribute the balance of the specimen evenly between two screw-top sterile polystyrene or polypropylene tubes. Specimens with gross blood should have 0.25 mL of sodium heparin (1,000 units/mL) aseptically added immediately to each tube. Note the addition of heparin on the tube. An additional 3.0-5.0 mL of specimen is needed if FISH testing for common aneuploidies is desired, refer to Prenatal Aneuploidy Screen
. Keep specimen at ambient temperature and transport within 24 hours.