Level II Ultrasound in Midpregnancy

When Should You Do a Fetal Anatomy Survey

Pregnant woman holding an ultrasound photo
Photo © Blend Images/Getty Images

An ultrasound is done in many a pregnancy around the mid part of a pregnancy. This is typically known as the fetal anatomy survey or the fetal anomaly screen. You will normally have this done when you are 18-22 weeks pregnant.

The way this ultrasound (or sonogram) is done is you will have a full bladder before the start of the exam. Your ultrasound technician will have you lay back on a table. Your pregnant belly will have a special gel placed on it to help enhance the picture from the sound waves of the ultrasound. The technician, or in some cases the physician, will use the ultrasound transducer wand and move it over your abdomen.

Images will appear on the screen. Some of the images will be measured and recorded. Many times you will be given some of the images to keep for fun. Some places will even let you record the session on a DVD. (This varies doctor to doctor, be sure to ask before your appointment, in case they require you to supply the DVD.)

Some of the things that they will look for will help them determine things about your baby and your pregnancy. They may look at the size of your baby in comparison to others babies of the same gestational age or they may look at your placenta.

Fingers and Toes

23 Weeks 3D Ultrasound
Photo © Lue and Krystal Vang

We often talk about how the first thing we'll do after our baby is born is to count fingers and toes. Now ultrasound technology can enable us to count fingers and toes prior to the birth. Though being able to count each finger and toe can depend on how cooperative your baby is being during the ultrasound exam.

Baby Limbs - Legs

3D Ultrasound Photos 24 Weeks Pregnant - Ultrasound Photos
Photo © A. Phillips

It is more likely that you will be able to see bigger areas like your baby's limbs - arms and legs. Your ultrasound technician will measure your baby's thigh bone (femur), the tibia and fibula. These will also help calculate how well your baby is growing for his or her gestational age.

Baby Limbs - Arms

3D Twin Baby B - 18 Week Ultrasound
Photo © M. Horn

In addition to look at the legs, they will also measure parts of your baby's arms. The bones of the arms (radius, ulna) are measured when possible.

Baby Brain and Stomach Ultrasound

Baby Brain Ultrasound
Baby Brain Ultrasound. Photo (c) K. Harrell

As the ultrasound progresses they will move to internal structures. It is amazing what they can see inside the baby. The brain is one thing that they can see. It often has a very butterfly looking appearance. They are looking for the presence and fullness of the baby's brain. They may also note any anomalies found, like choroid plexus cysts.

They will also look at the stomach, the urinary tract, kidneys and other structures during the ultrasound. If problems are found they will be followed with other ultrasounds, usually conducted by specialists.

Baby Spine Ultrasound

20 Week Spine Ultrasound
Photo © K. Harrell

The spine of your baby will also be looked at during the fetal anatomy survey. This is to see if the spine and neural tube are completely formed and without cysts.

Baby Heart Ultrasound

Baby Heart Ultrasound
Baby Heart Ultrasound. Photo © K. Harrell

During the ultrasound your ultrasound technician will do a through view of the baby's heart. They will measure the baby's heart rate and look for problems with the baby's heart including defects in the ventricles and other heart anomalies. If they suspect a problem with your baby's heart, they will most likely recommend a fetal echocardiogram or fetal ECHO.

Placenta and Umbilical Cord Ultrasound

Placenta Ultrasound
Placenta Ultrasound. Photo © K. Harrell

Looking at a picture of the placenta in ultrasound is also very interesting. They will look for where the placenta is located to ensure that you don't have a placenta previa. They will also note whether or not you have a three vessel cord. A normal umbilical cord will have two arteries and a vein. Occasionally you will see that some babies are born with a two vessel cord, also known as a Single Umbilical Artery. This can indicate some heart problems, though most of these babies will have a fetal ECHO and be born perfectly healthy.

Sex of the Baby Via Ultrasound

17 Week Ultrasound Photo - It's a boy! - Ultrasound Photos
Photo © J. Rauch

In the general time frame of the fetal anatomy scan, the sex of your baby is usually viable. How accurate the prediction depends on many factors, including the cooperation of your baby.


3D Ultrasounds

18 week 3D ultrasound
Photo © M. Horn

3D ultrasound is starting to be used more often. Many parents find the images more friendly than the stark black and white photos of the 2D pictures that standard ultrasound uses. Though it can be more difficult to obtain really good 3D photographs. Talk to your practitioner about the benefits of 3D versus 2D for your fetal anomaly screen.

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