Definitions

Prenatal Diagnosis

Is defined as a diagnosis suspected/made in a live fetus at any gestation

Prenatal Screening

Involves non-invasive tests for identifying fetuses who may be at higher risk of eg. Down Syndrome. Those women whose pregnancies
have been identified at higher risk may opt for a diagnostic test such as CVS or amniocentesis

Gestational Age at Discovery

Is the gestational age at which the fetus was first suspected to be malformed (excluding soft-markers) and indicates the time of the
examination rather than the time when the result is known (see Guide 1.3)

For definitions of terms used in prenatal screening and diagnosis the following link may be helpful

http://www.screening.nhs.uk/glossary-c