when to know baby's gender ultrasound

At how many weeks of pregnancy can you find out your baby’s gender?

After you get pregnant, you and your partner may get curious to know about the gender of your baby, one of the most exciting parts of your pregnancy. In addition, “is it a girl or a boy?” is one of the first questions of family and friends to a pregnant woman.

There are some early baby gender prediction methods used by old wives to determine if you are having a boy or a girl. Actually, the Internet is full of myths and fairy tales about it, including:

You are having a boy if:

  • Your baby’s heartbeat is lower than 140 beats per minute
  • You are carrying low or all out front
  • You are blooming in pregnancy
  • You didn’t suffer from morning sickness
  • You crave protein or salty food

You are having a girl if:

  • Your baby’s heartbeat is faster than 140 beats per minute
  • You are carrying high or all round
  • You are missing blooming in pregnancy
  • You suffered morning sickness
  • You crave sweet things

Although trying to predict your baby’s gender can make for a whole lot of fun, there is no real experimental evidence to confirm or deny these old wives’s tales and offer only a 50/50 chance of being accurate. Therefore, these tales should be taken with a pinch of salt and other methods, such as ultrasounds, should be used to find out your baby’s gender.

When can you find out your baby’s sex by ultrasound?

Most pregnant women find out their baby’s gender (if parents want to know) before the birth during their mid-pregnancy ultrasound, at around 20 weeks. However, sometimes the ultrasound technician can’t tell what the baby’s sex is on ultrasound if the baby is not cooperating in a position that doesn’t allow the sexual organs to be seen. In that case, you would have to wait until another ultrasound later in your pregnancy to find out the gender.

know baby's gender sex boy or girl week pregnant

Why should you wait until week 20 to find out your baby’s gender?

Although your baby’s sexual organs begins forming at 6 weeks, boy and girl babies look very similar on ultrasound until about 14-16 weeks. At this point it becomes more distinguishable but it isn’t always obvious and it can still be hard to differentiate them. Generally, by week 18, the ultrasound technician should be able to clearly identify the sex if the baby is cooperating.

Therefore, when it comes to your dating scan, at around 12 weeks, it is too early and ultrasound technicians are sceptical about the likelihood of an accurate prediction, even the most experienced sonographers.

Boy or girl? How babies’s sexual organs develop?

Your baby’s gender is determined at the moment of conception. Girls typically have an XX pair of sex chromosomes and boys an XY pair. The gender will depend on the sex chromosome carried by the sperm cell that fertilizes the egg.

Both, boys and girls develop in exactly the same way and have identical gonads and genital parts until around the eighth or nine week of gestation, when the genital tubercle begins to develop into a penis or clitoris as you can see in the next video:

Therefore, you wont’t be able to clearly start seeing the differentiated sex organs until 14 or 15 weeks. Actually, the testes in men are equivalent to labia and ovaries in women, and the penis is the equivalent of the clitoris. Interestingly, all babies would develop female genitals if it weren’t for the male hormone testosterone.

As you can see, at early pregnancy, a male and female genital tubercle can look very similar:

Photo credit: Marjorie England

Now you can see the problem in determining your baby’s gender before 20 weeks. It is not because ultrasound technicians can’t zoom in close enough the genitals, it is because all babies look like a baby boy.

What are ultrasound signs of having a boy or girl?

An ultrasound at around 18-20 weeks into the pregnancy is the most reliable way to tell a baby’s gender. It is called the fetal anatomy ultrasound and it is done to look for fetal anomalies, not simply to find out the sex of your baby.

At 20 weeks, the ultrasound technicians may examine your baby’s genitals and look for different signs, which suggest whether the baby is a girl or a boy:

Boy: The Turtle Sign

You will know the baby is a boy if the image shows a small protrusion with the shape of turtle between the legs. Don’t confuse with the umbilical cord that is also shown at the same location:

Girl: The Hamburger Sign

No sign of protrusion between the legs of the baby should be detected. Instead, it shows a hamburger-like structure with three white lines in between the legs, representing the clitoris and labia:

Boy Ultrasound wrong: How could a girl be mistaken for boy?

We all know people who was told boy at 15 weeks scan and baby was born a girl. Actually, ultrasound technicians tend to over-predict boys more often than girls. This can happen, for example, if the baby is developing slowly and the tubercle hasn’t begun to point up or the umbilical cord could be between the legs and be mistaken for a penis.

Girl ultrasound wrong: How could a boy be mistaken for girl?

It is very importante to know that the absence a penis at early stages doesn’t automatically make the baby a girl. Therefore, it is very important to make a positive diagnosis, not a diagnosis of exclusion, as a boy can very easily get mistaken for a girl. To tell the correct gender, the ultrasound technician should find the ultrasound signs of having a girl: The hamburger sign with three white lines.

Can you know if a baby is a girl or boy before the 12 weeks ultrasound?

Yes, as early at around 10 weeks of pregnancy, a non-invasive prenatal test (NIPT) can be performed. NIPT is a simple blood test that analyzes the baby’s DNA in the mother’s blood (yes, your blood contains fragments of DNA from your baby) and can identify the risk of chromosomal abnormalities such us Down’s syndrome, Edwards’ syndrome and Patau’s syndrome with 95-99% accuracy.

In addition, NIPT poses no risk to the baby and can also identify the sex of your baby as early as 10 weeks. Although extremely accurate at determining your baby’s sex, it is not 100% precise. The only way to know it for sure before birth is with an invasive diagnostic test like amniocentesis or chorionic villus sampling.

Images: Pixabay and Freepik


  1. Is this really correct? Most of the technicians predict the gender at 13 weeks and so on. So they can be wrong? According to text, all babies at 13 weeks should look like a boy?

  2. Can baby girl part be swollen due to hormones be confused for a boy??

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