History of Prenatal Testing

Prenatal tests were first introduced in the mid-1960s due to the discovery of the chromosomal mutation associated with Down Syndrome. The mutation that causes Down Syndrome is a trisomy in chromosome 21, which means that instead of the normal 2 copies of this chromosome, there is an extra copy which causes developmental issues in the child. Doctors and geneticists then realized they could study embryonic DNA by abstracting amniotic fluid from a pregnant woman-this procedure is known as amniocentesis. Early on, doctors would only conduct amniocentesis on women who were older than 35, because they were at higher risk of a child with a chromosomal anomaly. This process can be used to test unborn babies for genetic diseases such as Down Syndrome, Tay-Sachs disease, sickle cell disease, thalassemia, cystic fibrosis, neural tube defects, and a variety of chromosomal disorders. The discovery of this type of genetic test was the foundation for the establishment of several more genetic testing procedures founded in the past decade. 
Below is a chart depicting the types of prenatal tests and the risks/benefits of each: 

Below is a timeline that spans from pre-conception to post-pregnancy and identifies the times when certain prenatal tests/screens would take place: