<unk>  is the<unk>  of a disease or condition in a fetus or embryo before it is born. The aim is to detect birth defects such as neural tube defects, chromosome abnormalities, genetic diseases and other conditions.  It can also be used to determine the sex of the unborn baby.
Diagnostic prenatal testing can be by invasive methods or non-invasive methods. An invasive method is when probes or needles are inserted into the placenta, e.g. amniocentesis, which can be done from about 14 weeks gestation, and usually up to about 20 weeks and chorionic villus sampling, which can be done earlier (between 9.5 and 12.5 weeks gestation) but which is slightly more risky to the unborn child. 
Non-invasive methods, called "screens", can only evaluate risk of a condition and cannot determine 100% if the fetus has a condition. Non-invasive techniques include examinations of the mother's womb through ultrasonography and maternal serum screens (i.e. Alpha-fetoprotein)
If an abnormality is indicated by a non-invasive procedure, a more invasive technique may be employed to gather more information.
Prenatal diagnosis
Fetal screening
Birth control
Pregnancy test
Prenatal care
Peripartum mood disturbances screening
Hydrocephalus screening
Down syndrome screening