Twin Test – What You Need To Know

Upon hearing the news of having twins, a whirlwind of emotions and thoughts immediately begins. The mixture of joy, excitement, and anxiety, along with countless questions, create a storm that engulfs one’s mind.

Some of the big questions are “Will my Twins be healthy?” “I wonder if they will be fraternal or identical?” “What is the real difference between fraternal and identical twins, and why is it important?”

In the eye of the question tornado, this article will help differentiate between fraternal and identical twins and what types of testing can provide the best answers for your and your growing family. 

What is twin zygosity testing?

A twin zygosity test is a DNA test confirming whether twins are fraternal or identical. Twin zygosity testing compares twins’ DNA to examine if they are a match. An exact match means the twins are identical, and a partial match indicates the twins are fraternal. This DNA test can be done at any age. 

Twin zygosity testing can provide peace of mind for parents and children alike.

Understanding and knowing whether twins are identical or fraternal can give answers to medical, mental, and emotional health questions, such as disease risk, tissue compatibility, diagnosis, and more.

In addition, the power of knowing if a twin is identical or fraternal can equip the twins with a positive sense of identity and encourage sibling bonding.

So how can we access zygosity testing, and is it safe? Let’s break it down below. 

Zygosity Testing

Twin zygosity testing is a DNA test that confirms if twins are fraternal or identical twins. Identical twins share the same genetic makeup while fraternal twins share about half.

Twin zygosity testing not only provides answers to the DNA makeup of your twins but can also provide insight into medical and physical indicators and risks.

Providing the answer of identical or fraternal can also increase mental and emotional well-being while supporting positive self-esteem and a sense of identity. 

Understanding Twin Zygosity Testing

The term Twin Zygosity Test seems intimidating and can bring on a flood of questions all on its own. “Will it be painful?” “Who am I doing this for?” “How much does it cost?”

Twin zygosity testing is a simple DNA test, pain free, widely available, and can put the big question of Identical or Fraternal? to bed. 

How Is It Administered?

Zygotic testing can be completed on cells found in the amniotic fluid, cheeks, blood, and other tissues. The most common method for test administration is a “cheek swab.”

During this form of administration, a DNA sample is collected by using a buccal swab to collect a small DNA sample from the inner cheek. 

What Exactly Does It Test For?

Zygosity testing compares genetic markers from DNA samples. A DNA sample is like a “genetic blueprint,” each individual being unique. If < 99% of genetic markers match, the twins are identical, and if half of the markers match, the twins are fraternal. 

How Long Do the Results Take?

Results on average take 7 business days; however, results can be made available as early as 3 – 5 business days

How Accurate Is Genetic Testing for Twins?

Genetic Testing for twins is 99.99% accurate, and the risk for error is conclusively diminished by the DNA being run twice while at the lab.

Can the Twin Test Be Performed in the Womb?

The Twin Test can be performed in the womb; however, noninvasively it is inaccurate, and invasively it could cause a risk to the pregnancy in addition to having a higher risk of inaccuracy.

The most accurate and safe way to perform the Twin Test is after birth.

What About NIPT Testing for Twins?

An expecting mom talking her obstetrician in the office.

Non-Invasive Prenatal Testing (NIPT) is a method of testing used to assess the risk of a baby being born with genetic conditions. It is also used to determine fetal sex.

NIPT testing requires a blood draw that tests the mother’s DNA for certain chromosomes and looks for indicators to suggest any fetal abnormalities. The blood test is often paired with an ultrasound.

NIPT testing in twins has a much lower accuracy rate than in single fetal pregnancies and carries a higher risk for a false positive or negative.

Accuracy is increasing along with scientific advances, making NIPT testing a vital part of every pregnancy and providing peace of mind. The most accurate test for identifying fraternal or identical twins remains twin zygosity testing after birth. 

Can NIPT Differentiate Between Fraternal and Identical Twins? 

NIPT testing can be an indicator and support differentiation between twins in the womb. It looks at the number of placentas and the number of fetuses in the womb in addition to the number of chromosomes. 

What Does NIPT do?

A NIPT test is vital for every pregnancy. It is safe and provides many answers, even erroring on the side of caution.

Being able to tell if your twins share a placenta, share an amniotic sac, how many fetuses are in the womb, etc. will help assess pregnancy and fetal risk as well as address any fetal conditions. 

Is NIPT Worth Exploring?

NIPT testing is worth exploring. Partnering NIPT testing with twin zygosity testing after birth is an extremely accurate way to determine if twins are fraternal or identical.

By partnering with these testing types, you are supporting health and wellness during and after your twin pregnancy. NIPT testing should be a staple in every woman’s pregnancy single or multiples. 

How Much Does a Twin Zygosity Test Cost?

Costs for tests vary across companies however on average the cost for twin zygosity testing ranges from $79 to $400. Many of these DNA test kits are available online and even in large retail stores. 

Twin DNA Test Kit

Most at-home twin DNA test kits involve a “cheek swab.” Each kit commonly includes instructions, two sterile buccal swabs per person, sample envelopes or tubes, a consent form, and a prepaid label.

At-home DNA test kits are simple and straightforward. Each twin will have a buccal swab, and a parent will rub the buccal swab on the inner cheek of the child and place the swab inside of a personal sterile envelope or tube.

After the test is complete, the consent form will need to be signed and inserted into the prepaid return envelope along with the DNA samples. Once the samples are sent away, results take between 3 and 7 business days and are 99.9% accurate.

At home, DNA test kits are convenient and give accurate answers. There are a variety of test kits available that can be purchased on your budget. 

Genovate DNA Twin Test

Genovate DNA test kits are available online or in stores. They are highly accurate and extremely fast, producing results within 3 days. Genovate DNA tests cost on average about $150 for a twin test kit and consist of taking a “cheek swab.”

This DNA test is discrete, painless, can be done at any age, and provides quick and accurate answers.

How Soon Can You Tell if Twins Are Identical or Fraternal?

It is possible to find out if you are having twins at your 12-week pregnancy scan, and many families can be informed via ultrasound if the twins share a placenta or each have their own, which is an indicator for identical or fraternal twins. However, it’s not full-proof.

Throughout the pregnancy you can use NIPT testing or amniocentesis to gain more insight into your twins’ genetic makeup; again accuracy in the womb isn’t 100%.

NIPT methods for twins have less accuracy than for single pregnancies, and amniocentesis is an invasive procedure that comes with its own set of risks to the pregnancy.

Trying to determine identical or fraternal twins in the womb can be a rollercoaster and still be inaccurate.

The earliest you can tell for sure if your twins are fraternal or identical is after delivery when a DNA test or membrane analysis can be administered. 

How To Tell if Twins Are Identical or Fraternal?

One of the most common questions parents of twins receive is “Are they identical?” Here is how to tell if twins are identical or fraternal. 


Identical twins happen when a single egg is fertilized and splits in two. Identical twins are always same-sex twins. Fraternal twins happen when two separate eggs are fertilized and implanted in the womb. 

Genetic Testing

Identical twins share < 99.9% of the same DNA markers while fraternal twins share about 50%. Twin zygosity testing conducted after birth is the most accurate test to tell you if your twins are identical or fraternal. 


Generally, identical twins share a placenta as fraternal twins have two separate placentas.

So it is possible, if your first ultrasound scan is conducted before 14 weeks, that the tech can tell which placenta your twins have, giving you an indication of what type of twins you are carrying.

Placenta testing after birth is very accurate and always uses tissues to be examined for DNA marker comparison to conclude what type of twins you have. 

Fraternal Twins Ultrasound

All fraternal twins are Di/Di (dichorionic diamniotic), meaning each twin has a set of sacs and placentas. Essentially each twin is growing like a singleton, just a little more crowded due to sharing a womb.

If an ultrasound shows that you are carrying one of each gender, the twins are fraternal. 

Identical Twins Ultrasound

Identical Twin ultrasounds can be tricky as identical twins can also be Di/Di, Mo/Di (monochorionic diamniotic), and rarely even Mo/Mo (monochorionic monoamniotic).

Mo/Di twins share an outer chorionic sac and a placenta; however, they have their own amniotic sacs. Mo/Mo twins are quite rare and a little more high-risk because the twins will share one sac and one placenta.

Identifying identical twins in the womb is complicated, and ultrasounds have limitations. If both twins are the same gender and Di/Di, it will be extremely difficult to get a conclusive answer of identical or fraternal.

Ultrasounds are also less and less accurate the further along in the pregnancy a woman is. As previously stated, if an initial ultrasound is conducted before 14 weeks, a doctor can have a better insight. 

Related Questions:

Can Identical Twins Have Separate Sacs and Placentas?

Yes! It is common for identical twins to be Di/Di, making differentiating between identical and fraternal twins in the womb difficult and not without error. 

Can Fraternal Twins Be The Same Gender?

Yes! Fraternal twins are two eggs fertilized by two sperm and are often referred to as two singletons sharing a womb. They will share half their genomes just like any other siblings. 


Identical or fraternal your twins are double the happiness. Knowing whether your twins are fraternal or identical is double the confidence in understanding and nurturing your children’s mental, emotional, and physical health.

Sharing the truth behind your twins’ identical or fraternal identity will create a dual bond among siblings and promote positive self-esteem. Double the answers, double the peace of mind.