The frequency of feral malformations accounts for around 3~5%, and evaluation for the health of the fetus and screening for fetal malformations have become an important part of prenatal cares. Fetal malformations can be classified into structural and chromosomal abnormalities. Improvements in prenatal diagnosis have allowed identification of malformations in fetuses during the first and second trimesters of pregnancy. In prenatal diagnosis, both screening and diagnostic procedures are included. Screening rests include maternal serum aneuploidy screening tests, which are triple marker tests and quadruple test. Recently, first trimester combined ultrasound-biochemical screening and integrated screening was introduced and provided higher detection rates of chromosomal anomalies. Diagnostic tests are usually performed when screening results are positive, and they include chorionic villi sampling, amniocentesis, cordocentesis and fetal cells in maternal blood and preimplantation genetic diagnosis (PGD). In this review, we describe prenatal screening test, genetic diagnosis and its clinical significance.