When Is It Possible to Determine Gender by Ultrasound? Signs, Photos, and Errors

One of the most exciting moments of pregnancy for parents is when they can see their baby's gender through an ultrasound. But did you know that early gender diagnosis can be fraught with many errors and even mislead experienced doctors? Scientifically, determining gender with an ultrasound is somewhat possible from week 14 of pregnancy using the "Nub Theory," but the precise and reliable time is between weeks 18 and 22 during the anomaly ultrasound. In this timeframe, diagnostic accuracy ranges from 80% to 95% and depends on factors like the fetus's position, the amount of amniotic fluid, the thickness of the mother's abdominal wall, and the sonographer's experience. In the remainder of this article, we thoroughly review the types of gender diagnostic ultrasounds, the physical signs of boys and girls in ultrasound images, factors affecting diagnostic errors, and the difference in accuracy between ultrasounds and laboratory methods like NIPT. For specialized consultation and coordination for advanced ultrasounds at top medical imaging centers, you can contact Raadina Health Medical Tourism Company.

How is Fetal Gender Determination with Ultrasound Performed?

An ultrasound uses high-frequency sound waves to take pictures of the inside of the mother's uterus and abdomen. A specialist doctor observes the fetus's organs in the image, particularly its genitals, and diagnoses its gender.

In a male fetus, the scrotum and penis will usually be visible. In a female fetus, the structure of the labia and clitoris is observed. In the early weeks of pregnancy, the genitals of male and female fetuses look similar, making diagnosis a bit difficult. However, 2D, 3D, and even 4D ultrasound machines are currently used to increase accuracy.

How Accurate is Gender Determination with Ultrasound?

The accuracy of a gender-determining ultrasound ranges between 70% and 99%, depending on various factors. The mother's age, machine accuracy, and doctor's expertise are among the most critical factors determining accuracy. Gender accuracy based roughly on gestational age is shown in the table below:

From Which Week is Gender Determination with Ultrasound Possible?

Scientifically, the fetal genital nub becomes visible from about eleven to twelve weeks. At this time, a doctor can make an initial guess regarding the fetus's gender by examining the angle of the nub relative to the spine. If the angle of the genital nub to the spine is more than 30 degrees, the fetus is highly likely a boy. If the angle is smaller, the probability of a girl is higher. Of course, keep in mind that gender determination during this period has the lowest accuracy.

Gender Determination in NT Ultrasound

The primary goal of performing an NT ultrasound is to evaluate the risk of chromosomal abnormalities like Down syndrome. This ultrasound is usually performed between weeks 11 and 13. Although its main purpose isn't gender determination, the doctor can guess the fetus's gender by examining the angle of the genital nub.

Gender Determination in Anomaly Ultrasound

The anomaly ultrasound is considered the most accurate and vital ultrasound for determining fetal gender. This ultrasound is typically performed between weeks 18 and 22 of pregnancy, during which the doctor can see all the fetus's organs, such as the brain, heart, kidneys, spine, and genitals. According to information published on the reputable RadiologyInfo website (link provided in the sources), the accuracy of this ultrasound reaches over 95%.

Best Time for Accurate Fetal Gender Diagnosis with Ultrasound

According to a report by the American Medical Association, the best time for accurate gender diagnosis with ultrasound is weeks 18 to 22. During this period, the internal organs of the fetus are fully formed, and the gender can be identified with high accuracy.

Mandana, 28, says she was so eager to find out her baby's gender that she had an ultrasound before the eleventh week. The doctor told her the fetus was very likely a boy. Mandana bought boy-specific items and clothes, but her next ultrasound at 18 weeks revealed that the fetus was a girl!

How Are Boys and Girls Identified in an Ultrasound?

A doctor can diagnose gender from the image of the fetus's genital area. In a male fetus, the penis and scrotum will be visible as a distinct protrusion between the legs. In some medical terms, this shape of the male genitalia is called the "Turtle Sign," as it resembles the head and body of a turtle in certain views.

In a female fetus, the genitals appear as three parallel white lines, known as the "Hamburger Sign." These three lines represent the labia and clitoris. Naturally, viewing the genitals of either a boy or girl fetus is only possible when the fetus is positioned properly in the womb.

The Difference in Heart Rate Between a Boy and Girl Fetus in Ultrasound (Fact or Myth?)

One of the most common old beliefs among people is that the heart rate of a female fetus is faster than that of a male. Many believe that if the fetal heart rate is 140 beats per minute or higher, it's a girl, and if it's lower, it's a boy. However, scientific studies and a recent article published in the Journal of Maternal-Fetal Medicine confirm that there is no significant correlation between fetal heart rate and gender.

Fetal heart rate has nothing to do with gender. Credible scientific research shows that fetal heart rate depends on factors such as the fetus's activity level, gestational age, physiological factors, and fetal health.

What Factors Make Gender Diagnosis Difficult in Ultrasound?

Although ultrasound is the most accurate method for determining fetal gender, certain factors can sometimes make diagnosis difficult. The most critical of these factors include:

• Low Gestational Age: If you have an ultrasound before week 12, the diagnosis will be prone to error due to the incomplete formation of the genital area.
• Poor Fetal Position: If the fetus is turned toward the uterine wall, has its legs crossed, or the umbilical cord is positioned in front of the genital area, diagnosing gender becomes difficult.
• Maternal Obesity and Abdominal Wall Thickness: If the mother is significantly overweight, it is harder for ultrasound waves to pass through, resulting in lower-quality images.
• Low Amniotic Fluid: Amniotic fluid fills the space around the fetus and plays a vital role in image quality. If the fluid is low, image quality decreases.
• High Fetal Movement During Ultrasound: Some fetuses are very active during the ultrasound, preventing the doctor from capturing a clear and accurate image of the genital area.
• Quality and Technology of the Ultrasound Machine: Not all ultrasound machines have the same quality. Older machines have lower accuracy and quality, and vice versa.
• Sonographer's Skill and Experience: Specialized and experienced doctors can often diagnose fetal gender more accurately even in poor fetal positions.
• Multiple Pregnancies: Gender determination is usually harder in multiple pregnancies. The fetuses' proximity to one another, overlapping body parts, and finding the right angle make diagnosis difficult.
• Placenta Position: Sometimes the placenta's location can restrict the doctor's view and negatively impact imaging quality.
• Rare Genital Abnormalities: In very rare cases, the genitals have abnormalities and their shape doesn't perfectly match male or female patterns. In such cases, the doctor will prescribe additional tests for further investigation.

Margin of Error in Gender Determination with Ultrasound

The probability of error in ultrasound gender determination depends on various factors, the most important being gestational age. If you have an ultrasound before the eleventh week, the margin of error is extremely high. The error probability between weeks 11 and 13 is 15% to 30%. The ultrasound error rate from week 18 onwards will be less than 5%.

Gender Determination Error in Anomaly Ultrasound

Currently, the anomaly ultrasound is considered the most accurate method for determining fetal gender. When this ultrasound is performed, the fetus's internal organs are fully formed, and the gender determination error rate is less than three percent. Nevertheless, factors like human error, poor ultrasound machine quality, improper fetal positioning, and others can increase the margin of error.

Interpreting the Ultrasound Report and Fetal Gender Determination

You should always leave the interpretation of the ultrasound report to a specialist doctor, but with a little information, you can interpret it to a limited extent yourself. If the phrase "Not determined" is noted, it does not mean there is a problem; it simply means the imaging conditions were not suitable for an accurate diagnosis.

Ultrasound Image of a Boy and Girl Fetus

The ultrasound printout is black and white but clear and distinct. To make a better diagnosis, the doctor usually focuses on and highlights the genital area. In a female fetus, the genital area appears as three parallel white lines on the ultrasound image. In a male fetus, the genital area looks like a protrusion between the legs.

Why is Fetal Gender Not Visible in Early Ultrasounds?

In the early weeks of pregnancy, the fetus's internal organs—especially the sexual organs—are not fully formed, and it's impossible to tell whether it's a boy or a girl. Additionally, the angle of the genital nub with the spine cannot be viewed and measured. During the first few weeks, the fetus also moves more, making diagnosis harder.

Does Fetal Position Affect Gender Diagnosis in Ultrasound?

Yes, the fetus's position is one of the most critical factors in diagnosing gender via ultrasound. Diagnosis will be difficult in any of the following situations:

• The fetus's back is facing the ultrasound probe.
• Its legs are closed.
• It is positioned in a twisted manner.
• The umbilical cord is between the legs.

In some cases, the doctor may ask the mother to walk for a few minutes and then repeat the ultrasound. If there is no change, the ultrasound is scheduled again for the following days.

If Ultrasound Accuracy Isn't Enough for You, What Options Exist?

Note that an ultrasound only diagnoses the gender of the already formed fetus and has no impact on selecting your desired gender. If you want to determine your child's gender before pregnancy, methods like IVF and IUI exist. In the IVF method, you can select your child's gender with a success rate of over 99%. The IUI method is another approach that, while not as definitive as IVF, increases the probability of having a child of a specific gender by up to 60%.

Conclusion

Determining and diagnosing fetal gender during pregnancy is done using an ultrasound machine from the eleventh week onwards. The diagnostic accuracy of an ultrasound depends on various factors, including gestational age, maternal obesity, the machine's accuracy, and the doctor's expertise and experience. However, the accuracy of fetal gender diagnosis from the 18th week onwards will be over 95%. The key thing to understand is that ultrasound is strictly a diagnostic tool—it does not play any role in determining or selecting gender. For gender selection, other assisted reproductive techniques, such as IVF or IUI, are required.

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Frequently Asked Questions

Is it possible for an ultrasound to diagnose the fetal gender incorrectly?

Yes, especially if the ultrasound is done in the early weeks or if the fetus is in a poor position, the chance of a mistake is high.

Why do doctors sometimes not state the gender definitively?

Because the margin of error always exists, particularly if the fetus is positioned poorly, making it impossible to clearly see the genitals.

Is gender determination with an ultrasound more accurate than a blood test?

Both methods have high accuracy, but a blood test using DNA increases accuracy to 99%.

Can the fetal gender change in subsequent ultrasounds?

The fetus's gender does not change, but the initial diagnosis might have been wrong, and a subsequent ultrasound might state a different gender.

Is a 3D ultrasound better for determining gender?

In some cases, yes, because it shows more detail, but generally, no.

If two ultrasounds yield two different results, which one is more reliable?

If taken at the same time, consider the doctor's expertise and experience, as well as the machine's accuracy. But if taken at different times, the ultrasound done at a later gestational age—especially between weeks 18 and 22—is more reliable.

Does the doctor's skill play a role in determining gender?

Yes, the doctor must have sufficient skill and expertise to diagnose the fetal gender even in cases of poor fetal positioning.

Why is gender determination recommended at week 12?

Because at this time, the internal organs have grown enough, and the angle between the genitals and the spine will be clearly visible.