The Basics

Down Syndrome Facts National Association for Down Syndrome (also in Spanish)

Genetics

Down Syndrome: Causes Mayo Clinic

Mosaic Down Syndrome

MDS FAQs International Mosaic Down Syndrome Association

Physical Development

A Healthy Start National Down Syndrome Society

Prenatal Testing

Down Syndrome: What You Need to Know When You're Pregnant American Academy of Family Physicians (also in Spanish)

Trisomy 21

Down Syndrome (Trisomy 21) Lucile Packard Children's Hospital, Stanford CA