A paternity test can be done as early as 7 to 9 weeks into pregnancy using a non-invasive prenatal paternity test, which involves a blood sample from the mother and a mouth swab from the alleged father. This test analyzes fetal DNA in the mother's bloodstream and poses no risk to the mother or baby. For testing after birth, a paternity test can be done immediately, even within the first day after the baby is born, using a simple cheek swab from the newborn and the alleged father. For legal purposes, a paternity test after birth may require a legal chain-of-custody sample collection. Prenatal testing before 7 weeks typically is not available or accurate, and invasive prenatal testing options exist but carry risks and are not recommended solely for paternity testing.
