These days, it's pretty much routine for pregnant women in their second trimester to be scheduled for a level 2 ultrasound, more commonly called the 20-week anatomy scan. That's because practitioners have found that this special pregnancy ultrasound is a great way to see how a baby is developing and offer reassurance that everything is going exactly the way it should be.

The 20-week anatomy scan is a fascinating opportunity to get a sneak peek of your baby — and fun to take home a souvenir photo to start the baby album. Here's what you can expect during your appointment.

What is the 20-week anatomy scan?

The American College of Obstetricians and Gynecologists (ACOG) says that women should get at least one sonogram in the second trimester of pregnancy, and virtually all practitioners now order an ultrasound anatomy scan for their moms-to-be. At this appointment, a trained sonographer will perform a detailed anatomy scan.

Even if you had a first-trimester (level 1) sonogram to confirm or date your pregnancy, or as part of a first-trimester screening test, the more detailed level 2 sonogram is important because of all the additional valuable information it gives your practitioner about what's going on with your baby.

True to its name, the 20-week anatomy scan is performed in the second trimester of pregnancy, and can be done anytime between 18 weeks and 22 weeks.

If you have a condition that needs to be monitored (such as carrying multiples), you may have more than one detailed ultrasound.

What does the 20-week anatomy scan look at?

A level 2 ultrasound focuses closely on fetal anatomy to be sure everything is growing and developing as it should; images are much clearer and more detailed than the fuzzy ultrasound you might have gotten in your first trimester. Here's what the sonographer will be looking for:

  • Measuring your baby's size and checking all major organs: Your baby will be measured from crown to rump, around the middle, and around the head, and his weight will be estimated. The four chambers of the heart will be looked at, as well as the kidneys, bladder, stomach, brain, spine and sex organs. The sonographer will also look at the fetal heart rate.
  • Help screen for some genetic disorders: A level 2 scan also checks for hard and soft markers, characteristics that may indicate an increased risk of a chromosomal abnormality. Important to know before you head into your scan: Very few babies showing soft markers (choroid plexus cyst, echogenic foci or pyelectasia, to name an unpronounceable few) end up having an abnormality. Your practitioner will let you know whether any follow-up testing is necessary (it often isn't).
  • Telling you your baby's sex (if you want to know): Be aware that a level 2 ultrasound can also tell you the sex of your baby if you haven't already found out through noninvasive prenatal testing (NIPT) or a CVS, though with less than 100 percent reliability and depending on baby's cooperation. Remember: Be sure to tell your sonographer if you don't want to know!
  • Estimating the amount of amniotic fluid in your uterus to make sure the level is normal. The sonographer will also be looking at your amniotic fluid levels and the location of the placenta.

What happens during the 20-week anatomy scan?

Many parents-to-be find that the second-trimester ultrasound is fun to watch. Before your appointment, you may need to drink water so you'll have a full bladder, which makes it easier to take ultrasound images.

When it's time for your exam, you'll recline on an exam table with your tummy exposed, and a sonographer will apply gel and then move a wand (transducer) over your abdomen. As sound waves emitted from the transducer bounce off internal organs and fluids inside, a computer converts them into a 2-dimensional image (or cross-sectional view) of the fetus on a screen. Sometimes 3D or even 4D ultrasound technology is used instead of 2D.

To get the most comprehensive anatomy assessment, the sonographer will be aiming for many different views from lots of different angles. When the technician gets a clear shot, they will freeze-frame the picture (that's the actual sonogram) and measure a specific part of the body. During the scan, you may be able to spot your baby's beating heart, the curve of the spine, and the face, arms and legs. You may even catch sight of your baby sucking a thumb!

Settle in to enjoy the show: The detailed level 2 scan can take 30 to 45 minutes (depending on how cooperative your little one wants to be). The perinatologist and your practitioner will review the rest, and you will likely go home with at least one or two sonogram pictures. 

Does the 20-week ultrasound have any risks?

There are no significant risks associated with ultrasounds, though medical guidelines caution against unnecessary exposure to ultrasound — which is why your practitioner will schedule only a handful of them throughout your pregnancy.

If you're concerned about the upcoming picture show (and what those grainy images reveal), talk to your practitioner about what they are looking for. Chances are you'll come away enlightened (and relieved).

Routine second trimester ultrasounds are usually done in 2D. Most practitioners reserve the more detailed 3D and 4D ultrasounds for when they’re medically necessary to more closely examine a fetus for a suspected anomaly.

 While ultrasound technology is considered very safe, practitioners prefer to be extra cautious and minimize intrusions into your womb.