The 20-week ultrasound is an important milestone in your prenatal care. Not only does it mark the “halfway point,” but it also provides a detailed look at fetal development and insights into maternal health (that’s yours!).

Because of this particular scan’s significance, there are understandably many common questions about what to expect, many I still hear after 20 years of ultrasound experience. As a key part of your prenatal care, it’s great to be informed.

Purpose of the 20-week ultrasound

Fetal development

The 20-week ultrasound is a vital screening tool that helps healthcare providers assess fetal anatomical structures and maternal health, ensuring everything is developing through pregnancy as expected.

At this stage, the fetus is large enough for detailed evaluation, making it easier to check for any potential concerns with vital organs—some of which aren’t fully developed until 18 weeks.

Maternal health

In addition to evaluating the baby’s development, the scan evaluates maternal health by checking the uterus, cervix and ovaries.

More on that below!

Timing of ultrasounds

As with all of pregnancy, timing is everything. At WHA, there are two ultrasounds during pregnancy that are fairly typical.

Depending on when you begin to receive prenatal care, your unique health history and your pregnancy, you may have fewer or your provider may recommend additional ultrasounds. Sometimes additional ultrasounds may be needed if we’re not able to capture everything we need because of the fetus’s gestational age or position.

  • First trimester – To confirm the due date of the pregnancy and perform genetic screening if desired.
  • Second trimester – To look at the fetal anatomy in detail, around 20 weeks.
  • Additional – As indicated for certain medical conditions or genetic screening.

Preparing for the 20-week ultrasound

When preparing for your 20-week ultrasound, be sure to drink 24 ounces of water 30 minutes before your prenatal ultrasound exam. This helps with visibility of maternal structures; if needed, a vaginal ultrasound exam may be performed for clearer assessment of certain structures.

What to expect during the 20-week ultrasound

Knowing what to expect during your ultrasound helps ensure a smooth process. The 20-week anatomy scan typically lasts about 60 minutes, and we ask that you arrive 10 minutes early before your appointment.

During the scan, the sonographer will focus on different organ systems. For many people, they’re understandably hard to see and interpret. While sonographers are trained extensively to do this, sometimes we may get quiet as we concentrate on getting all the required images and fetal measurements. Don’t let this worry you! We are just trying to focus and take the most accurate images.

Plus, the fetus doesn’t always get in the exact position we need when we need it. So the sonographer may ask you to change positions, cough or even take a bathroom break to help the fetus move.

If we have a tough time viewing specific structures, we’ll note that in the report, and your healthcare team will provide further guidance based on these observations. The sonographer’s role is to gather all of the information, so the maternal-fetal medicine specialists can interpret it after the ultrasound.

Minimizing distractions

To minimize distractions and ensure a smooth ultrasound, we ask that you bring no more than one or two support people and for these adults to take a break with any children present if they get fidgety or upset.

Also important to note is we cannot allow any recording in the exam room. This is to protect patient privacy.

Anatomical features and measurements assessed

We begin by imaging your cervix to assess its length. The cervix helps the fetus stay safely in the uterus for the duration of pregnancy. As the pregnancy progresses, especially closer to labor, the cervix will gradually soften, shorten and eventually open to allow the baby to be born.

We also document the placenta, its relationship to the cervix and where the umbilical cord connects to the placenta. We measure the amount of amniotic fluid. Additional images are taken of your ovaries and uterus to assess the wellbeing of your reproductive organs.

Next, we assess organ placement, cardiac motion, and then take a bathroom break so you can empty your bladder!

Then we continue with a thorough examination of the fetal anatomy from head to toe. This includes looking at the:

  • brain
  • spine
  • heart (the size of a thumbnail!)
  • abdominal organs
  • face
  • limbs, including fingers and toes

We also measure the baby’s head, abdomen, and upper leg and upper arm bones. These prenatal ultrasound measurements help track the baby’s growth.

Post-scan process

After the scan, your ultrasound is sent to one of WHA’s maternal-fetal medicine specialists. These physicians have additional training and experience interpreting obstetric ultrasounds. They will complete a detailed ultrasound report interpretation and share the final results with your provider who will share them with you.

Remember, it’s perfectly okay to ask questions during your appointment and engage with your healthcare team throughout the process. The 20-week ultrasound is a crucial part of your pregnancy, providing valuable insights into the health and development of both you and your baby. So your team is here to support you and make sure you have a positive and informed experience.