PregnancyHealth and SafetyWhat to Expect at Your 20 Week Anatomy Scan

What to Expect at Your 20 Week Anatomy Scan

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If your Anatomy Scan appointment is coming up, you’ve made it to the second trimester and (hopefully) past the early pregnancy woes such as morning sickness, fatigue, etc. For this reason, some call the second trimester of pregnancy the ‘golden period’ – women typically have more energy than they did in the beginning, but also haven’t yet reached the point of swollen feet, difficult sleep, and other discomforts that a large, third trimester belly brings.

Sometime between 18-22 weeks, you’ll have the Anatomy Scan. During this visit, your doctor will perform an ultrasound that takes a close look at your baby’s development. You’ll definitely want to take home pictures from this one!

Your baby at 20 weeks

Your baby has grown quite a bit since the 10 week ultrasound and is about the size of a mango. He or she is weighing in at around 10 ounces and the crown to rump length is around 6.5 inches.

In terms of development, baby is making great strides by this point. Your little one is developing taste buds and even swallowing amniotic fluid – some research even suggests preferences to certain foods are being formed!

He or she is now covered in a substance called vernix caseosa, which is a waxy, cheese-like substance that protects his or her soft skin from irritation from the surrounding amniotic fluid and is designed to keep baby warm after birth.

Hiccups? If you’re noticing your stomach quaking every so often, your baby may have the hiccups. Don’t worry, this is totally normal.

By now, you should have started to feel fetal movement. Talk to your doctor about whether or not they recommend kick counts and how often. You may notice your baby is the most active at night; some say this is because when you are walking around all day baby is lulled to sleep, so nighttime is when he or she wants to party!

The Anatomy Scan ultrasound

Now that your uterus and baby are big enough, this ultrasound will be done abdominally (rather than transvaginally). Your doctor will apply gel directly to your abdomen and slide a rounded transducer over your lower abdomen.

Your doctor will go organ-by-organ and ensure each part of your baby’s body is developing properly. Besides the crown to rump length, he or she will measure the abdominal and head circumference along with the length of certain bones such as the femurs. A closer look will also be taken at the heart (to make sure the four chambers are present and functioning) as well as the brain, stomach, kidneys, bladder, spine, and sex organs.

Interestingly, if you’re having a girl, your baby’s uterus has already developed, and she is already carrying eggs in her tiny ovaries. That’s right – your uterus is carrying another uterus! If you’re having a boy, the testicles will still be in his abdomen, waiting to descend into the scrotum once it develops.

Another thing your doctor may mention is that he or she is looking for a three-vessel cord. A normal umbilical cord will have two arteries and one vein; the arteries carry waste away from the baby to be filtered through your kidneys, and the vein is responsible for delivering oxygen and nutrients to the baby.

If you didn’t already find out the baby’s sex during your prenatal screening labs, your doctor will be able to reveal it at this visit, if desired. If you and your partner are choosing to keep the sex a surprise until birth, be sure to remind your doctor or ultrasound tech so that they don’t slip in any pronouns or anatomical terms that might spoil the surprise!

As with previous ultrasounds, you should be able to listen to baby’s heartbeat, which should be beating at a rate of 110-160 beats per minute.

What will your doctor be looking for?

There are certain congenital defects that can be found during the 20-week scan. These may include (but are not limited to):

  • Markers for Down Syndrome or other chromosomal abnormalities
  • Congenital heart defects
  • Cleft palate
  • Spina bifida
  • Renal agenesis (having only one kidney)

Your doctor will also take a look at the location of your placenta to screen for a condition called placenta previa. Placenta previa is a condition in which the placenta is partially or completely covering the cervix (the opening of the uterus). If you’re told you have placenta previa during your Anatomy Scan, try not to stress too much – your doctor will simply order another ultrasound to be done closer to the third trimester. Your uterus will be changing quite a bit between now and 40 weeks, so that placenta has lots of time to move. If it doesn’t, your doctor will recommend a scheduled Cesarean section instead of a vaginal birth.

As with other ultrasounds, you may be feeling nervous to hear unexpected news. Breathe easy: most anatomy scans result in totally normal results. If this isn’t the case for you, know that the beauty of the anatomy scan is to allow for you and your medical team to plan for best outcomes for your baby.

What else can you expect from this visit?

Starting around this time, your provider will start to measure your fundal height, which is the length from your pubic bone to the top of your uterus. Starting at 24 weeks, this length in centimeters should equal the gestational age of your baby (e.g. at 30 weeks, your fundal height will be 30cm).

If they haven’t already, your provider will likely fill you in on the Glucose Tolerance Test that is coming up. Done around 28 weeks, this test involved drinking 50 grams of a very sweet glucose drink and then having your blood drawn exactly one hour later to check glucose levels. The results will indicate whether you might have developed Gestational Diabetes, which is a condition that can form in pregnancy and can be dangerous for your baby.

Tip: if your doctor’s office gives you the drink to bring home, refrigerate it! The drink tastes much better cold than it does at room temperature.

What about the other ultrasounds?

After the Anatomy Scan, you will likely only have one more routine ultrasound before meeting your baby in person. The last ultrasound will be a few weeks before your due date and will provide estimates for your baby’s weight and the amount of amniotic fluid you are carrying. Additionally, it will confirm your baby’s positioning.

For now, celebrate making it to the halfway point!

Read More of Our Series on Ultrasound Scans

The Viability Check Ultrasound Scan

The 10 Week Ultrasound Scan

The 20 Week Anatomy Scan

The 37 Week Ultrasound Scan

Routine blood tests during pregnancy: Our guide to the blood tests you’ll be recommended during pregnancy

Written by

Abigail Purcell, RN
Abigail Purcell, RN
Abigail is one of our expert writers and is a BSN, RN (Registered Nurse) with a wide range of experience. She has worked in Public Health, Medical-Surgical nursing, and, most recently, Paediatrics and Women’s Health. Her true passion is serving mothers and families by helping them navigate their healthcare. As a nurse writer, Abby enjoys being able to empower patients on a larger scale, using evidence-based information that is easy to access and understand.


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