A phlebotomist will be sent to any location in the United States to collect the blood sample. Sample identifiers will be removed as the first step so that laboratory personnel will not see or have access to identifiers. No information will go back to patients or their physicians.

If less than two fetal cells are recovered from maternal blood, a redraw is indicated

Outcome 1 is the number of cells identified as fetal by microscopic staining. This can be converted to units based on volume. If 40 mL of blood is collected and f8 cells are designated as fetal based on microscopic staining, the results can be tabulated as follow: So a result is 8 cells are identified as fetal from one blood draw. This equals 0.2 cells identified per mL of maternal blood. If two or fewer cells are obtained, a blood redraw will be requested from the patient.

Outcome measure 2 is the number of cells that yield high quality next generation sequencing data suitable for determining copy number across the entire genome. So if 4 of the 8 cells above gave high quality data, the outcome would be 4 cells with high quality copy number data from one blood draw which equals 0.10 high quality cell / mL of mother's blood.