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How to Read Your Paternity Test Results: Timing and Accuracy

How accurate are paternity test results? Learn how to read and understand paternity test and DNA test results so you can be certain they're correct.
Paternity Test
Updated: June 27, 2023

If you’re not sure who the father or your baby is, or want to know if a child is yours, paternity tests can give you peace of mind.

A paternity test is a crucial tool in establishing the biological father of a child. In recent years, advances in genetic testing technology have made paternity tests more reliable. When performed correctly, paternity tests give highly accurate results in a matter of days.

However, understanding paternity test results can be confusing for many people. In this article, we will discuss the different types of paternity tests, how they work, their accuracy, and the timeframe for results.

Related: 6 Traits Babies Inherit From Their Father

Why Paternity Matters

There are several reasons why both parents may want to know who the biological father of the child is, other than simply wanting to know whose name to list on the birth certificate.

A man may wish to know so that he can choose to be involved in his child’s life. If he’s unsure, a legal test may give him peace of mind. Sometimes potential grandparents may want to know whether to be involved in their son’s potential child’s life as well.

Mothers may want to know who their child’s father is so they can ask for support, whether for emotional or legal purposes. In some cases, a paternity test may be court-ordered to determine whether a man needs to pay child support.

Paternity tests can also be used to legally prove kinship, for immigration purposes. If you need a paternity test for this reason, look for one that has accreditation from the American Association of Blood Banks (AABB), such as the DNA Diagnostics Center (DDC).

How Paternity Tests Work

Paternity tests use genetic testing to compare a sample of your baby’s DNA to that of an alleged father or fathers. The testing process measures a series of genes in the DNA profile and looks for how many genes match between the baby and possible father.

When a child is conceived, the mother and father each pass half of their genetic code via their gametes (sperm and egg).

Let’s break down the science of conception a bit further. Every cell in the human body contains two copies of each gene or allele. However, generally only one of these genes or a blend of the two will present in the person.

For example, you can carry a blue-eyed allele but you may have dark eyes. But you can still pass a blue-eyed allele to a child.

The only cells in the body that do not carry two copies of each allele are the sperm and egg cells, which each copy one. This is so that the newly-created person will end up with a total of two copies—one from the mother and one from the father.

How Paternity Tests Work

Paternity tests measure the length of every allele in a child’s DNA and that of the suspected biological father. Since a father passes half of his genetic code to any child he conceives, comparing both DNA lines should show that about half or more are a match.

You will notice that the sex chromosomes (amelogenin sex genes) are listed on the test as well. These, however, are not compared.

This is generally used as a quality control measure. If the sex marked is correct for both father and child, we can be more confident that the results are accurate.

How Do I Read My Paternity Test Results?

When you receive paternity DNA test results, your eyes will likely skim down to the end of the report which states the conclusion. It will either say that you are definitely not the father, or that there is a possibility that you are.

If your results show a combined paternity index of 0, you can be sure you are not the father. However, if the combined paternity index shows a number, you probably are.

Generally, you are the father if the test shows any probability of paternity. The results are based on how much more likely you are to be the father than an unrelated man from the same racial background.

These tests can never guarantee that you are the father, because to do so they would have to compare your DNA to every other man on the planet — and obviously, that’s not possible.

But if you’re matching the child, you can safely assume that you are the father. The only exception would be if there’s a possibility that your brother or someone closely related could be the father as well.

Getting deeper into your results, paternity test results show each locus (location of the allele) and measurement for each. If you look through these measurements, you will see that about half of them or more are the same if you’re likely the father.

How Early Can You Take a Paternity Test?

Paternity tests can be taken during pregnancy. There are two types of tests that can be done while the child is still in gestation: Non-Invasive Prenatal Paternity Test (NIPP) or amniocentesis.

The NIPP test takes a DNA sample from the father and compares it to a sample of the mother’s blood. A baby’s DNA circulates in the mother’s blood, so you can get a sample collection this way.

Is it Dangerous to Have a Paternity Test While Pregnant?

Paternity Test While Pregnant

An amniocentesis takes a sample of amniotic fluid by inserting a needle into the mother’s abdomen and compares this with DNA collection from the father.

Amniocentesis comes with a small risk of harm to the baby including miscarriage, so it is not recommended by the American Pregnancy Association (APA).

If the NIPP test cannot be done, the APA recommends waiting until the child is born to do the test.

To test after birth, a sample can be taken directly from the umbilical cord. It’s also possible to take a buccal swab (cheek swab) or blood sample at a later date. This will be compared to the alleged father’s sample.

You can get a paternity test done while the mother is still pregnant, but it is advisable to choose a non-invasive test. If that test doesn’t work or cannot be done, it’s safer to wait until after the child is born to test.

What is the Time Frame for Paternity Test Results?

The turnaround time for paternity tests is relatively quick. Depending upon which company you choose, you can get results as soon as 1 to 2 business days after you submit the samples.

What Are the Odds of a Paternity Test Being Wrong?

It’s extremely rare for a DNA paternity test to give an incorrect result. If the results report shows that you match the child, you can safely assume that you are the father.

If your brother or another close relative of yours may possibly be the father, the test could be wrong. In this case, you would want to submit DNA from both or all potential fathers and let the testing company know that these men are closely related.

They will compare each man’s result and likely take additional measurements in the paternity test report to narrow down which man is the father.

In a situation where identical twin brothers both might be the biological father, there is no way to know which one is really through a DNA test. Identical twins have exactly the same DNA.

What Are the Different Types of Paternity Tests?

All paternity tests use a DNA sample from the child and the potential father or fathers. The different methods to take DNA samples include:

  • Non-Invasive Prenatal Paternity Test (NIPP)
  • Amniocentesis
  • Umbilical Cord Sample
  • Blood Tests
  • Cheek Swabs

You can do a home paternity test or you can send your paternity test kit with samples to a lab. If you are concerned about accuracy or you need the test for legal reasons, a lab will be the best choice.

What Is the Difference Between a Paternity Test and a DNA Test?

Paternity vs DNA

A DNA test analyzes a person’s genetic code to help them learn more about themselves. It may give them information about their genealogy or possible health conditions they are at risk for.

A paternity test has the specific goal of determining paternity. It compares a child’s DNA with a man’s DNA to see if that man has fathered that child. The focus is not on what specific traits are in the DNA, but how many of them match between the child and potential father.

How Many DNA Markers Are Used for a Paternity Test?

Paternity tests compare 15 to 20 genetic markers, depending on which testing company and which specific test you choose. Extended tests may test more than 60 markers. Markers are listed until “locus” which describes where in the DNA the marker is located.

What Happens if the DNA Test Is Not Conclusive?

It is truly rare for a DNA test report to be inconclusive when it comes to paternity, but it can happen. These tests are highly accurate because a child shares so much DNA (half) with their biological father.

If you do get an inconclusive result, you can repeat the test. There may have been an issue with one or both samples, or there may have been a problem during the testing procedures. You can try a company that tests for more markers if you want to try to get a more accurate result.

Elisa Cinelli

About Elisa

Elisa is a well-known parenting writer who is passionate about providing research-based… Read more

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