Learn about the accuracy of NIPT (Non-Invasive Prenatal Testing) for gender determination, including its high precision, safety, and the benefits of early testing. Discover why NIPT is a recommended option for expecting parents.
- When Can You Find Out the Baby’s Gender?
- Methods and Accuracy of Prenatal Gender Determination
- Why Can NIPT (Non-Invasive Prenatal Testing) Determine Gender?
- Accuracy of Gender Determination with NIPT (Non-Invasive Prenatal Testing)
- Is There a Possibility of Errors in Gender Determination with NIPT (Non-Invasive Prenatal Testing)?
- Can NIPT (Non-Invasive Prenatal Testing) Be Used for Twins?
- Is It True That Sometimes the Gender Is Not Revealed?
- Conclusion
When Can You Find Out the Baby’s Gender?
If no special tests are conducted, the gender of the baby is determined during routine prenatal checkups using ultrasound examinations. It is often possible to identify boys around 14-15 weeks and girls around 17-18 weeks, although this can sometimes be delayed if the fetus’s position makes it difficult to see.
In addition, prenatal diagnostics such as amniocentesis, chorionic villus sampling, and NIPT (Non-Invasive Prenatal Testing) can also determine the gender of the baby. When can the gender be determined using these methods? Each method is explained below.

Methods and Accuracy of Prenatal Gender Determination
There are several tests that can determine the gender of the baby before birth, including ultrasound examination, amniocentesis, chorionic villus sampling, and NIPT (Non-Invasive Prenatal Testing). Let’s take a closer look at each of these methods.
Ultrasound Examination
Ultrasound examination (also known as echography) is a method of determining the gender of the fetus by directing ultrasound waves at the mother’s body and visualizing the fetus based on the reflected data. This method includes 2D, 3D, and 4D types.
4D ultrasound adds the dimension of time to 3D imaging, allowing for real-time observation of the fetus’s condition. However, it cannot examine the movement of the heart or the internal organs.
Ultrasound examinations are performed during routine prenatal checkups. If the external genitalia of the fetus can be visualized, the gender can often be determined and disclosed to the parents.
In the case of boys, the external genitalia appear as a protrusion around 14-15 weeks. For girls, the external genitalia, resembling a leaf shape, become visible around 17-18 weeks. Sometimes, this can also be confirmed with ultrasound photos.
However, if the fetus’s position or orientation makes the external genitalia difficult to see, the determination may be delayed.
Amniocentesis
Amniocentesis is a test that involves first using ultrasound to accurately locate the fetus and placenta, then inserting a thin needle into the abdomen to extract amniotic fluid from the uterus. This fluid is analyzed to detect chromosomal abnormalities and determine the gender of the fetus.
Amniocentesis is influenced by the amount of amniotic fluid available but is generally performed between the 15th and 18th weeks of pregnancy. One of the key points is that it can determine the fetus’s gender with almost 100% accuracy.
Chorionic Villus Sampling
Chorionic villus sampling (CVS) involves either inserting a needle into the abdomen based on ultrasound images or using a catheter through the vagina to collect a sample of the chorionic villi, which are part of the early placenta.
The collected chorionic villi are then examined under a microscope to analyze the fetus’s chromosomes for chromosomal abnormalities and gender determination. Since only chromosomes are examined, it is not possible to detect all congenital disorders.
CVS can be performed between the 11th and 14th weeks of pregnancy, and it can determine the fetus’s gender with almost 100% accuracy.
Risks of Amniocentesis and Chorionic Villus Sampling
Amniocentesis carries a risk of miscarriage or stillbirth at a rate of 1 in 300, while chorionic villus sampling (CVS) has a risk of 1 in 100. Although both amniocentesis and CVS can determine the gender with nearly 100% accuracy, the associated risks are a significant concern.
NIPT (Non-Invasive Prenatal Testing)
NIPT (Non-Invasive Prenatal Testing) is a test that examines fetal DNA fragments present in the mother’s blood during pregnancy to detect chromosomal abnormalities in the fetus.
This test, introduced in 2013, is notable for its ability to detect chromosomal abnormalities in the fetus with minimal burden, as it only requires a blood sample from the mother. Although it is a non-diagnostic test, it has a very high negative predictive value, meaning the likelihood of false negatives is very low.
Additionally, in non-certified facilities, gender determination may be available as an option.
NIPT (Non-Invasive Prenatal Testing) provides high accuracy in gender determination and can be performed solely through a blood test, posing no risk of miscarriage.
Another significant feature is that the test can be conducted as early as the sixth week of pregnancy.
Why Can NIPT (Non-Invasive Prenatal Testing) Determine Gender?
Gender is determined by the combination of sex chromosomes. Boys have XY chromosomes, while girls have XX chromosomes. NIPT (Non-Invasive Prenatal Testing) can determine gender by analyzing fetal DNA fragments obtained from the mother’s blood, allowing for the examination of sex chromosomes.
Accuracy of Gender Determination with NIPT (Non-Invasive Prenatal Testing)
Since NIPT (Non-Invasive Prenatal Testing) analyzes fetal DNA fragments, it can determine gender with a very high accuracy of 99.9%.

Is There a Possibility of Errors in Gender Determination with NIPT (Non-Invasive Prenatal Testing)?
It is important to note that while this test can determine gender with 99.9% accuracy, it is not a foolproof method. Although it is a very safe procedure and can be conducted very early in pregnancy, there is still a 0.1% chance that the determined gender could be incorrect.
For instance, if the presence of a Y chromosome is detected, there is a 99.9% likelihood that the baby will be a boy. However, it may not always be clearly confirmed through ultrasound, and in very rare cases, there could be issues such as malformation of the external genitalia.
Therefore, it is essential to understand that gender cannot be determined with 100% certainty, and this should be considered when opting for the test.
Can NIPT (Non-Invasive Prenatal Testing) Be Used for Twins?
It is natural to wonder if the test can be performed when it is known that you are expecting twins. The answer is yes, it is possible to take the test with twins. However, the test can only be performed for twin pregnancies and cannot determine results for pregnancies with three or more fetuses. Additionally, the availability of the test may vary depending on the facility.
If the test results are positive, and the twins are identical (monozygotic), there is a possibility that both twins may have genetic congenital abnormalities. If the twins are fraternal (dizygotic) and the result is positive, it cannot be ruled out that one or both of the twins may have congenital abnormalities.
Can NIPT (Non-Invasive Prenatal Testing) Determine the Gender of Twins?
NIPT (Non-Invasive Prenatal Testing) determines gender by the presence or absence of the Y chromosome. Therefore, in the case of twins, if only X chromosomes are present, it can be determined that both are girls. However, if the Y chromosome is present, it cannot be determined whether both are boys or if there is one boy and one girl.
Is It True That Sometimes the Gender Is Not Revealed?
While NIPT (Non-Invasive Prenatal Testing) can determine the gender of the baby, there are cases where the gender will not be disclosed. This is because the Japan Society of Obstetrics and Gynecology does not recommend disclosing the gender.
Therefore, certified (accredited) NIPT facilities do not offer gender determination, but many non-certified facilities do provide this service.
Additionally, even if you choose a plan that includes gender determination, you have the option to decide whether or not you want to know the gender.
Conclusion
Before deciding whether to find out the baby’s gender before birth, it’s important for couples to discuss their preferences. Knowing the gender in advance can make it easier to plan and purchase baby items. On the other hand, not knowing the gender until birth can increase the excitement and surprise at the time of delivery.
If you want to know the gender early, taking the NIPT (Non-Invasive Prenatal Testing) is recommended. NIPT can determine the baby’s gender with high accuracy and is conducted through a blood sample from the mother, posing no risk of miscarriage or stillbirth. It is considered the safest prenatal test. Previous methods, while safe, had lower accuracy and carried some risk of miscarriage or stillbirth.
NIPT does not have such issues, making it a recommended test for pregnant women who want a safe and more accurate prenatal diagnosis. It can be considered by anyone, regardless of age. If you want to know your baby’s gender before birth, you might consider NIPT.
Q&A
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QHow many weeks does NIPT reveal the gender?The test can be performed after the 6th week of pregnancy.However, it is generally recommended that the test be taken after 10 weeks of pregnancy.
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QWhat do you mean by 99.9% accuracy in determining gender with NIPT?Because it analyzes DNA derived from the fetus, it can determine sex chromosome combinations very accurately.However, a 0.1% error margin exists.
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QWhat is the likelihood that the NIPT gender determination will be wrong?As the 99.9% accuracy indicates, mistakes are very rare, but misjudgments can occur with a probability of about 0.1%.
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QWhat is the method used to determine gender with NIPT?Gender is determined by analyzing sex chromosomes (X or Y chromosomes) from fetal-derived DNA in the mother's blood.
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QHow is gender determined by NIPT in the case of twins?The presence or absence of a Y chromosome determines whether at least one is a boy or not, but does not provide detailed individual sex determination.
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QIs there a risk of miscarriage with NIPT gender determination?No, NIPT is a non-invasive test that only requires a blood sample from the mother, and there is no risk of miscarriage.
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QWhat if I do not want to know the gender in NIPT?It is possible to request that the health care provider not reveal the gender of the patient prior to testing.
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QHow soon will I know the results of the NIPT gender determination?It generally takes one to two weeks from the time of testing to receive the results.
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QDoes NIPT provide gender determination at any facility?Some facilities certified by the Japanese Society of Obstetrics and Gynecology may not provide gender determination, while some non-certified facilities provide it.
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QIs there an additional charge for NIPT gender determination?Depending on the facility, an additional fee may be charged if gender determination is an option.
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QWhat else can NIPT tell us besides gender determination?Chromosomal abnormalities such as 21 trisomy (Down syndrome), 18 trisomy (Edwards syndrome), and 13 trisomy can be examined mainly.
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QCan the gender be accurately determined even at 6 weeks gestation?Although the test is highly accurate, low levels of fetal-derived DNA may require retesting.
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QWhat should I do if the gender determined by NIPT is different from the ultrasound?Final confirmation will be made after birth, but in some cases other testing methods can be used to confirm the results.
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QAre there any conditions or restrictions for taking NIPT?In Japan, some facilities offer the test regardless of age or pregnancy progress, but conditions may differ from facility to facility.
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QWhat are the advantages of having NIPT gender determination in advance?In addition to making it easier to prepare childcare supplies, it also makes it easier to design lifestyles after the birth.
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QIs it possible to have NIPT just for gender determination?It is possible at some non-certified facilities, but is usually offered as part of a test intended to test for chromosomal abnormalities.
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QIf I am not satisfied with the gender determination results of NIPT, should I try another method?正確性は高いですが、完全ではありません。他の方法として羊水検査や絨毛検査を検討することも可能です。
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QWhat are the causes of cases of incorrect gender determination results?Insufficient concentration of fetal-derived DNA or contamination of maternal-derived DNA may be the cause.
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QDo I need a doctor's permission to determine gender with NIPT?Prior explanation and consent may be required depending on the facility's policy and the physician's judgment.
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QWhat is the difference between NIPT and other gender determination methods?NIPT is noninvasive, can be performed early, and is highly accurate.On the other hand, amniocentesis and chorionography are risky but provide near 100% accuracy.
Learn about the accuracy of NIPT (Non-Invasive Prenatal Testing) for gender determination, including its high precision, safety, and the benefits of early testing. Discover why NIPT is a recommended option for expecting parents.
Article Editorial Supervisor

Dr Hiroshi Oka
NIPT specialist clinic, MD
Graduated from Keio University, School of Medicine