Prenatal diagnosis and prenatal screening are aspects of prenatal care that focus on detecting anatomic and physiologic problems with the zygote, embryo, or fetus as early as possible, either before gestation even starts (as in pre-implantation genetic diagnosis) or as early in gestation as practicable. It is a way for a doctor to determine, before birth, whether the fetus has a problem such as Down syndrome. The screening focuses on finding problems among a large population with affordable and noninvasive methods, whereas the diagnosis focuses on pursuing additional detailed information once a particular problem has been found, and can sometimes be more invasive. Screening can also be used for prenatal sex discernment. Amniocentesis and chorionic villus sampling (CVS) are tests that help find genetic disorders before birth. Common testing procedures include, ultrasonography including nuchal translucency ultrasound, serum biomarker testing, or genetic screening. In some cases, the tests are administered to determine if the fetus will be aborted, though physicians and patients also find it useful to diagnose high-risk pregnancies early so that delivery can be scheduled in a tertiary care hospital where the baby can receive appropriate care.