What Is An Anatomy Ultrasound?

When the pregnancy hits the 20th week of gestation, an anatomy ultrasound is often ordered. This sonogram is used to determine fetal anomalies, the baby's size and weight, and also to measure growth to ensure that the fetus is developing properly.

By the 20th week of pregnancy, the baby can weigh up to 11 ounces and measure 10 inches outstretched. The fetus has fingerprints, tiny arms and legs, and the genitalia is often formed. The pregnant woman is beginning to “show” with a small baby bump popping out. The rate of growth from the 20th week until the 40th week will increase exponentially.

What Will The Technician Be Looking For?

Basically, the technician or the doctor will be looking for any signs of slower than normal development. The skeleton should be hardening at this point and the sex of the baby may be visible. In many cases, the baby may have their legs crossed or be facing away from the abdomen and thus the sexual organs will not be visible during the anatomy ultrasound.

What Will Happen During the Ultrasound?

After the pregnant woman is called into the ultrasound room, she will be asked to lie flat on an ultrasound table. Her full bladder may pose a bit of discomfort, but otherwise the ultrasound will be painless and likely enjoyable. The technician or doctor will apply a warmed gel to the abdomen and use a small paddle to scan the abdomen to take a look at baby inside the uterus. The following fetal parts are checked during the anatomy ultrasound:

  • Face
  • Brain (ventricles, choroid plexus, mid-brain, posterior fossa, cerebellum, cisterna magna, measurements of anterior and posterior horns of lateral ventricles)
  • Skull (shape, integrity, BPD and HC measurements)
  • Neck (nuchal fold thickness)
  • Spine
  • Heart (rate, rhythm, 4-chamber views, outflow tract)
  • Thorax (shape, lungs, diaphragm)
  • Abdomen (stomach, kidneys, liver, bladder, wall, umbilicus, cord, abdominal circumference AC)
  • Limbs (femur, tibia, fibula, humerus, radius, ulna, hands, feet femur length FL)
  • Genitals (gender, abnormality)
  • Cervix (length and opening)
  • Amniotic fluid
  • Placenta position and anomalies
  • Cervix

In addition, the examination includes a look at the adnexae of the mother to detect any abnormailties of the ovaries and fallopian tubes.

Based upon the results of the measurements, the gestational age of the baby will be calculate based upon the average size of other babies scanned during the 20th week of pregnancy. However, the range of calculations at this time of the pregnancy is within 2-3 weeks of the actual due date, while an earlier ultrasound is more reliable to calculate the due date. If any fetal abnormalities are found, additional examinations are indicated.

Pictures and Fun!

Many ultrasound technicians will print off various pictures of the face (and occasionally the sex organs) for mom and dad to enjoy. These pictures will vary based upon whether the scan completed is a 2D, 3D or 4D scan. More advanced ultrasounds can render a 3 dimensional picture of baby for mom and dad to enjoy.

Some anatomy ultrasounds will be performed on machines with video recording capabilities. If you wish to have a video recording of the ultrasound, make sure to ask the technician before beginning if that is a possibility.

The anatomy ultrasound performed in the 20th week of gestation is a time of pride, joy and a little anxiety. Some parents are looking to have a boy or a girl while others are simply happy to put a face to the movement inside their belly.

Read More:
Fetal Weight Calculator
Estimating Fetal Weight Via Ultrasound