Ultrasound Signs for Determining Baby's Sex

Absence of Penis = Girl Theory

One sign that mothers think automatically indicates a girl, for example, is the "Absence of Penis = Girl" theory. This theory states that if the ultrasound technician fails to find a penis the baby is automatically a girl.

You will see below there is more to a girl ultrasound picture than the absence of a penis. In fact, particularly early on in pregnancy, a clitoris and a penis are roughly the same size and shape.

Hamburger Sign

When doing an ultrasound to determine the sex of your baby, an ultrasound technician will actually look for girl genitalia—labia and clitoris. When these are seen, it is often referred to as the "Hamburger Sign."

The clitoris situated between the labial lips looks like a hamburger between two buns, or three lines. The labia would be the buns of the hamburger and the clitoris would be the meat.

Turtle Sign

When the ultrasound technician is looking for a boy, they are looking for something called the turtle sign. This is where you can see the tip of the penis peeking out from behind the testicles.

This may be harder to see with some babies, which is why there are multiple signs to look for during an ultrasound. The gestational age and position of the baby play a part in what can be seen.

Erect Penis

Even as a fetus, baby boys can and will have erections. If you happen to be looking with ultrasound during that time, you will see a very clearly defined penis. This obviously makes identifying a baby boy much easier.

Seeing an erection may bother some parents. But don't worry—it is normal for boys to have erections. You will notice these after birth as well, during diaper changes.

A Word From Verywell

The greater availability of 3D and 4D ultrasounds has changed how ultrasounds determine a baby's gender. Ultrasounds are often more accurate because you can see body parts more clearly, as opposed to guessing from shadows.

Remember, before 18 weeks the clitoris and penis are roughly the same size and can easily be mistaken. Although you understandably really want to know the gender of your baby and prepare for his or her birth, it's best to be patient. No matter what type of ultrasound you use, there will always be errors, especially with early ultrasounds.