When can Down syndrome be diagnosed?

Down syndrome can be diagnosed during pregnancy or after birth, making this answer comprehensive and accurate. Prenatal testing methods, such as non-invasive prenatal testing (NIPT), chorionic villus sampling (CVS), and amniocentesis, can identify the presence of Down syndrome before the baby is born. Additionally, after birth, healthcare providers can make a diagnosis based on physical characteristics commonly associated with Down syndrome, and a definitive diagnosis can be confirmed through genetic testing, such as karyotyping.

This dual possibility of prenatal and postnatal diagnosis reflects the understanding that Down syndrome can be detected at various stages, taking advantage of advancements in medical technology and genetics. The other options are less complete as they limit the timeframe or methods for diagnosis only to specific scenarios, which does not encompass the full range of diagnostic opportunities available.