The most common and reliable paternity test method is DNA testing. The discovery of DNA was a huge leap toward understanding heredity and the way our parents’ biology directly influences our own, since DNA is the ultimate “source code” of the human race.

And since we get our genetic makeup directly from our parents–half from each parent–it is easy to determine whether a man is the biological father of a child based on the comparison of the two DNA samples.

Most DNA-based paternity tests are postnatal, that is, they are performed after the child was born, with samples containing DNA taken from the child and the alleged father(s), and optionally, the mother.

Since every human cell contains a copy of the entire DNA of the person, these DNA samples can be gained in a variety of ways, including from blood, a cheek swab, the umbilical cord when the baby is born, saliva, semen, hair, or other piece of tissue.

There is the option for a prenatal paternity test as well, although the prenatal methods can sometimes pose some danger to the fetus and these procedures require the permission and help of an OB-GYN. The two main methods of prenatal paternity tests are amniocentesis and chorionic villus sampling, or CVS.

Amniocentesis involves the doctor using ultrasound to guide a needle through the abdomen into the uterus to get a sample of amniotic fluid, which contains the baby’s genetic material. During CVS, the doctor guides a needle up the vagina to collect pieces of tissue called chorionic villi off the walls of the uterus, which come from the fertilized egg and thus also have the baby’s DNA.

Given the samples of at least the child and an alleged father, DNA paternity tests are held to be 99.999% accurate.