Early blood tests now make finding out the sex of a baby possible toward the end of the first trimester. However, the results are not always 100% accurate. Anatomy scans during the second trimester are typically more accurate.

This article discusses when a person or couple can find out the sex of their developing baby and what factors may affect this timing.

Pregnant person seeing their baby's sex on ultrasound scanShare on Pinterest
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How quickly a person can learn the sex of their developing baby depends on various factors. This article details two main methods.

People used to have to wait until the midpoint of pregnancy, around the middle of the second trimester, when the genitals become visible on an ultrasound scan. Many pregnant people still choose this option.

However, today, a pregnant person can learn the sex of the fetus by having an early blood test. Healthcare providers can do this test toward the end of the first trimester, usually at about 10 weeks.

There is no failsafe method of determining the developing baby’s sex with 100% certainty. The only way to find out for sure is to wait until the baby is born.

However, amniocentesis and chorionic villus sampling (CVS) can produce a fairly accurate result because they involve looking at the sex chromosomes. And people who use in vitro fertilization (IVF) can choose their baby’s sex.

Most people find out the sex of their developing baby using one of two methods.

Noninvasive prenatal testing

Noninvasive prenatal testing (NIPT) uses bloodwork to assess the risk of a several genetic disorders. NIPT can also identify the sex because the test scans for the presence of a Y chromosome, the chromosome that generally results in a male baby.

According to one article, the test’s accuracy varies but generally hovers around 98–99% or higher. Typically, doctors usually perform the test toward the middle or end of the first trimester, at about 10 weeks or later.

Second trimester anatomy scan

A second trimester anatomy scan is a detailed ultrasound that helps a doctor or ultrasound technician see fetus’s organs, the location of the placenta, and determine the health of the developing baby and the pregnancy.

Healthcare providers usually schedule it within weeks 18–22 of the pregnancy.

At this time, the developing baby is usually large enough for the healthcare professional to see the genitals. A skilled technician can often identify the sex based on their appearance.

A 2012 study of two-dimensional ultrasounds found that technicians were slightly better at predicting male fetuses than female, with a 100% success rate for males compared with 97.9% for females.

A healthcare provider cannot always detect the sex with an ultrasound because the developing baby may be too small. Their position might not be ideal for viewing the genitals, or something might obstruct the technician’s view of the genitals.

When this happens, a healthcare professional might recommend coming back for another scan in a few weeks.

More invasive tests

If an anatomy scan shows potential problems with the fetus, a doctor may recommend additional, more invasive, testing.

According to Planned Parenthood, amniocentesis and CVS both involve taking samples of genetic material. Although these tests can accurately predict the sex of the developing baby, doctors carry out these tests to identify chromosomal abnormalities, such as Down syndrome. They do not routinely carry out these tests to determine sex.

Both tests can cause serious complications, so a person should not choose either method unless there is a medical reason to do so.

Some prenatal sex tests can determine the sex of a developing baby by identifying the external features while others detect the chromosomes.

NIPT blood testing

NIPT blood testing can detect chromosomes but may not predict the development of the genitals. For example, a newborn with male-typical XY chromosomes might have an unusually small penis that resembles a clitoris.

However, NIPT does not detect all chromosome abnormalities, so it may not identify that a fetus has an unusual chromosome pattern.


Ultrasounds look at the external genitalia of the developing baby. This means they cannot reveal information about chromosomes.

An ultrasound can give a technician a good idea about the sex of a developing baby. However, they are not always 100% correct.

However, ultrasounds cannot always identify if a developing baby has genitals or internal sex organs that fall outside the typical sex characteristics of a male or female.

Planned Parenthood explain that an intersex baby has internal or external sexual anatomy or chromosomes that are not typical of males or females.

For example, the baby may have the chromosomes of one sex and the genitals typical of another, or they may have an unusual pattern of chromosomes, such as XXY. Typically, females have XX chromosomes, and males have XY chromosomes.

A prenatal sex test may predict a baby’s sex but cannot predict their gender.

While sex is biological, gender is the social role with which the person ultimately identifies. Some people grow up to reject gender entirely, while others identify as nonbinary or as a different gender from the sex that healthcare providers assigned them at birth.

Parents should consider that sex does not necessarily predict a child’s gender. Moreover, neither sex nor gender identity necessarily reveal anything about the child’s eventual personality or preferences.

Furthermore, no prenatal sex testing is 100% accurate. Human error, unusual chromosomes, testing inaccuracies, and scientific knowledge all mean there is always a possibility of a surprise at birth.

Home prenatal sex tests aim to identify male-typical sex chromosomes in the pregnant person’s blood. If they are present, the results indicate the fetus is male. Otherwise, they indicate the fetus is female.

These tests often promise very high rates of accuracy, such as 99%. However, they have a higher potential for human error because of contaminated or inadequate blood samples.

It is important to note that medical authorities, doctors, and other health professionals have not validated these products. The Food and Drug Administration (FDA) have not approved their use.

Many folk legends suggest that the fetus’s position, heart rate, or the pregnant person’s food cravings may predict the sex. However, there is no scientific evidence to support that these prediction methods work.

Predicting the sex of a developing baby is becoming much more accurate. Still, even with the most accurate methods, there is room for error.

People who want to know the sex of their baby should discuss the risks and benefits of each option with a doctor.