Pregnant women with low risk indicators for fetal chromosomal aneuploidy will be enrolled. Study blood will be collected in the first or second trimester at a scheduled prenatal screening visit, processed to plasma, and stored frozen until analysis. Each pregnancy will be followed until delivery and the birth outcome recorded.

Inclusion Criteria:

• Pregnancy is 10-22 weeks gestation
• Between 18-34 years of age inclusive at estimated date of delivery
• No prenatal screening indicators for high risk including serum biochemical and ultrasound screening
• No personal or family history of Down syndrome
• Willing to provide written informed consent
• Willing to provide a whole blood sample
• Willing to provide access to medical records supporting fetal outcome

Exclusion Criteria:

• Fetal demise at the time of the blood draw
• Previous specimen donation under this protocol

Pregnant with low risk for fetal chromosome 21 aneuploidy

Upon analysis of collected samples and submission for publication, data will be shared as per journal requirements.