18 week ultrasound: What is your doctor checking for and what should you expect?

At 18 weeks, you’re halfway through your pregnancy. By this time, your baby has already developed all its major organs and structures, which is why it’s a common time for your second-trimester ultrasound.

An 18 week ultrasound is also known as the anatomy scan. The procedure is typically performed transabdominally and takes from 30 to 60 minutes to complete. In the process, the technician will measure your baby and assess its major systems for possible anomalies. They will also check for your placenta position.

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So, you are 18 weeks pregnant. This is approximately 5 months, meaning that you are halfway through your journey, and it couldn’t be more exciting. At this time, your baby continues growing rapidly, and so does your uterus and belly. So, you’ll likely look noticeably pregnant now. You may also prepare for some 18-week symptoms that might intensify, such as back aches, bloating and gas, leg cramps, and others. And there are many positive things to prepare for as well!

In particular, 18 weeks is about the time when you might have your mid-pregnancy scan scheduled. It’s an important milestone that allows for a detailed analysis of your baby’s anatomy and major systems. So, it can be equally exciting and stressful.

Of course, you might have plenty of questions as you prepare for your 18 week ultrasound. To help you reduce anxiety, we’ve prepared a detailed guide that will address common concerns and help you gain peace of mind.

What’s Happening in Your Body at 18 Weeks?

At 18 weeks, your baby completes several important developmental milestones:

• Bones that have been soft previously now begin to harden, or ossify. 
• The body is now covered in lanugo, which is a peach fuzz-like hair that protects the baby and keeps them warm.
• Although they’re still closed, your baby’s eyes also continue to develop. Now they are facing forward rather than to the sides and can react to light.
• Ears finally take their final position and now stand out from the fetus’s head. Around this time, your baby should also be able to hear.
• You may also start feeling movement. Although some mothers-to-be can experience the first fetal quickening as early as 13-16 weeks, many don’t feel it until 18 weeks.

All in all, 18 weeks is quite an exciting spot to be in during your pregnancy. There is still a lot going on in your body as your baby continues to develop. And your upcoming 18 week ultrasound will show you many important things, so it's natural to feel somewhat thrilled.

Is It a Common Practice to Schedule an 18 Week Ultrasound?

In a typical pregnancy ultrasound schedule, there are two core screenings:

• The first one is a viability and dating scan usually conducted between 10 and 13 weeks. During this screening, healthcare providers locate the fetus, determine the number of babies, and estimate the due date.
• The second scan is performed in the second trimester, between 18 and 22 weeks. It’s also known as the anatomy scan. During this screening, doctors check the baby’s organs and major systems, and might also check for any problems with the placenta or amniotic fluid.

As you can see from this schedule, it’s a rather common practice to get your ultrasound 18 weeks pregnant. It’s a routine screening, which is a part of the standardized prenatal care. So, there is absolutely nothing to worry about in relation to it.

At the same time, it’s important to understand that every pregnancy is unique. The specific schedule of your screenings and prenatal visits depends on many things, including your doctor’s practice, health condition, and medical/obstetrician history. That is, it’s absolutely normal to have more than two ultrasounds in your pregnancy or have them at different times.

18 Week Sonogram: Understanding the Full Anatomy Scan

As was mentioned earlier, an ultrasound performed between 18 and 22 weeks is known as the anatomy scan. So, what is it, in the first place?

In a nutshell, the anatomy scan is an important routine ultrasound. It’s a detailed screening, during which doctors assess the baby’s anatomy to confirm health and proper development. Some of the main things that doctors check for include:

• Heart
• Spine
• Limbs
• Brain
• Other major organs
• A detailed analysis 

Additionally, your healthcare provider will assess the placenta and the amount of amniotic fluid. All these details help check for any anomalies or birth defects that might be there.

What Anomalies Can the Doctor Detect in My Baby at 18 Weeks Ultrasound?

By 18 weeks, your baby has already completely formed its major organs and structures. Although they are not yet fully mature, they should be visible in an ultrasound, which allows for a very in-depth evaluation of your baby’s health.

During an 18 week ultrasound, doctors can detect a wide array of possible abnormalities with a fairly high accuracy. Some of the key anomalies that might be detected include:

• Thickened nuchal skin fold
• Cystic hygroma
• Meningoceles
• Nasal bone absence/hypoplasia
• Hypertelorism and hypotelorism
• Cleft lip
• Neck masses
• Echogenic bowel
• Fetal bowel dilatation
• Dysplastic kidneys
• And many others

The accuracy of detection might not be 100%. That is, not every abnormality might be seen clearly. However, it’s believed that the full anatomy scan helps detect over half of the major structural issues.

What to Expect From Your 18 Week Ultrasound

Typically, a normal 18 week ultrasound is performed transabdominally. You should already know how the process goes – the technician applies gel to your belly and moves a transducer around to receive an image. However, there might be a need for a transvaginal probe if the abdominal ultrasound is inconclusive or the doctor needs to get a clearer view of specific structures or measure your cervix.

During the process, your healthcare provider will occasionally stop the video to assess your baby’s organs and structures. The doctor might point out the head, heart, and other parts of your baby so that you see what’s going on. Also, good technicians typically comment on positive findings to give you peace of mind. However, you shouldn’t expect very detailed information during an ultrasound. It’s a standard practice to organize all findings in a detailed report that you will see later. Also, your healthcare provider should explain all the important points and answer your questions during a follow-up visit.

If there are any findings that require further investigation, your healthcare provider may refer you to a fetal medicine department specialist. Further investigation will help confirm or rule out any concerning findings.

How Big Is Your Baby at 18 Weeks Ultrasound?

By 18 weeks, your baby should be around 14.2 cm long. This is about the size of a bell pepper, which is big enough to offer you a clear ultrasound image.

When you have an ultrasound 18 weeks pregnant, you should be able to see your baby rather clearly. You can expect to see a distinguished head, torso, and limbs. Also, it’s already possible to differentiate your baby’s facial features and even notice movements and facial expressions.

Understanding Different Placenta Positions

During an 18 week ultrasound, your healthcare provider should also assess your placenta and tell you about its position, so it’s natural to wonder what it actually means.

These are the positions that you might see in your doctor’s report:

• Anterior placenta: This is the placenta that’s located on the front wall of the uterus. It’s a very common position that doesn’t affect your or your baby’s health in any way. However, it might affect how you feel fetal movement during pregnancy because it cushions the kicks because of its placement.
• Posterior placenta: This is the placenta that’s located on the back wall of the uterus, closer to your spine. It’s also very common and is often considered optimal because it allows you to feel your baby’s movement earlier and more strongly.
• Lateral placenta: This is the placenta that’s located on one of the uterus’s sides (left or right). It doesn’t affect fetal health or how you feel movement.
• Fundal placenta: This is the placenta that’s located at the top of the uterus. It’s often considered a “textbook ideal” position because its location allows for optimal blood flow and nutrient exchange. It also doesn’t create any risk of complications.
• Low-lying placenta: This is the placenta that’s located below the midline of the uterus. The placement of this placenta makes it partially cover the cervix, which can lead to a higher risk of bleeding and a C-section.
• Placenta previa: This is the placenta that covers the cervix partially or fully. It’s a more serious condition compared to the low-lying placenta, which almost always requires a C-section because it covers the opening through which the vaginal delivery occurs.

Most placentas are normal and lead to healthy pregnancies. The two exceptions are the low-lying placenta and placenta previa. These positions typically require monitoring and increase the risk of a C-section. However, don’t get worried just yet. These two positions only affect about 1 in every 200 births, so the chances of having them are very low.

If, after the scan, you learn that you have a low-lying placenta, it also shouldn’t be a cause for concern just yet. In most cases, it moves up as your pregnancy progresses, so there is a chance that the placenta will have a different position by the time you give birth. You will only need a C-section if it remains very close to the cervix.

In the case of placenta previa, it’s indeed a more serious condition that won’t go away on its own. But, even if you face it, you shouldn’t get overly worried because careful monitoring and adherence to the recommendations of your healthcare provider should help prevent complications and mitigate risks.

FAQ

How long does a normal 18 week ultrasound last?

Traditionally, an 18 week ultrasound lasts longer compared to your previous screenings because it’s much more detailed. You can expect it to last from 30 to 60 minutes. The exact timing depends on how well your baby cooperates with the doctor and what they will be able to see.

How accurate is gender prediction at 18 weeks?

Generally, the anatomy scan (between 18-22 weeks) is considered the perfect opportunity to detect your baby’s gender. By this time, the fetal external genitals should become more defined and clearly visible, which allows doctors to predict the gender with a fairly high (95-99%) accuracy. However, it’s important to remember that several things can affect the accuracy of gender determination, including the skills of the technician, image quality, and your baby’s position.

What does an 18 week ultrasound look like?

During this ultrasound, you will see a standard 2D, black-and-white image. You should be able to have a rather clear view of your baby at 18 weeks ultrasound. The head, torso, limbs, and facial features are already quite distinguishable, and it’s possible to observe facial expressions and movement.

Conclusion

As you now know, 18 weeks of pregnancy is a common time to have the full anatomy scan of your baby. This is one of the most important screenings that allows doctors to assess all major systems of the fetus and detect key anomalies. And it’s also the time when your healthcare provider can determine the baby’s gender with high accuracy.

After reading this guide, you know what to expect from your 18 week sonogram. Use it as a roadmap to prepare well and eliminate unnecessary stress.

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