This page provides a glossary of terms that may be helpful during your experience with Duke Perinatal.

Down syndrome: A type of mental disability caused by an extra chromosome #21. Down syndrome typically causes mild to moderate mental retardation and an increased chance of birth defects. Heart defects are the most common birth defect seen.

Trisomy 13 and 18: Types of mental disability caused by an extra chromosome #18. Trisomy 13 and 18 typically causes severe mental retardation and multiple birth defects. Most babies born with these conditions do not live more than a few months.

Chromosomal abnormality: Any condition caused by having too much or too little chromosome material. Chromosomes carry our genetic information.

Open neural tube defect: Any opening along the spine (spina bifida) or skull (anencephaly) that allows the nervous tissue to be exposed (not covered by skin.) Ranges in severity depending upon the location or size of the opening.

Screening test: Offers an estimation of a problem. Although they cannot determine the presence or absence of a birth defect with certainty, they offer more information about the probability. Examples are first trimester screening and testing done in the second trimester called triple or quad screening. This second trimester test is also sometimes referred to as the maternal serum screen or AFP test.

Diagnostic test: Determines with most certainty the presence or absence of a birth defect or chromosome problem. Examples include amniocentesis and chorionic villus sampling.