Signs Ultrasound Technicians Look For to Determine a Baby's Sex

1
Absence of Penis = Girl Theory

baby ultrasound
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If you have chosen to find out the sex of your baby, you are most likely going to do so via ultrasound. Typically, the ultrasound is done halfway through the pregnancy. It is called the fetal anatomy survey and it is done to look for fetal anomalies, not simply to find out the sex of your baby.

The accuracy of the report will depend on many factors, including the age of the baby, the equipment used, the technician, and the baby. However, there are certain signs in boy and girl ultrasound pictures that the technician uses to determine the gender of your baby.

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.

2
The Hamburger Sign (Girl)

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

3
The Turtle Sign (Boy)

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 into what can be seen.

4
The Erect Penis

Even as a fetus, baby boys can and will have erections. If you happen to be looking with an 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 ultrasounds has changed how ultrasounds determine a baby's gender. 3D ultrasounds are often more accurate because you can see body parts more clearly, as opposed to guessing from shadows.

No matter what type of ultrasound you use, there will always be errors, especially with early ultrasounds. 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.

Sources:

Hagen-Ansert, SL. Textbook of Diagnostic Sonography - E-Book: 2-Volume Set. Seventh Edition. 2011.

Manzanares S, Benítez A, Naveiro-Fuentes M, López-Criado MS, Sánchez-Gila M. Accuracy of fetal sex determination on ultrasound examination in the first trimester of pregnancy. J Clin Ultrasound. 2016 Jun;44(5):272-7. doi: 10.1002/jcu.22320. Epub 2015 Dec 11.

Odeh M, Granin V, Kais M, Ophir E, Bornstein J. Sonographic fetal sex determination. Obstet Gynecol Surv. 2009 Jan;64(1):50-7. doi: 10.1097/OGX.0b013e318193299b.

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