All About the 20-Week Ultrasound

The mid-pregnancy anatomy scan may be the most eagerly anticipated ultrasound of any you'll get as a parent-to-be. Find out what you'll see when you have yours.

For most parents-to-be, the 20-week anatomy ultrasound is their big chance to sneak a peek at their baby before his birth day. But this test can do more than let you glimpse your baby. It can give you and your doctor a sense of whether your baby looks healthy, or if there may be some issues that you'll need to prepare for before your baby arrives.

Is the 20-week ultrasound essential?

Not necessarily. "Large studies have shown that the mid-pregnancy or anatomy examination, which almost all pregnant women receive, does not significantly [affect] outcomes," says Michele Hakakha, M.D., an ob-gyn in Beverly Hills and author of Expecting 411. "But it is a routine exam and has been for many years."

What will we see in the ultrasound?

At this ultrasound, you may get a better sense of what your baby will look like -- and the determination of your baby's sex is usually obvious at this point. But there's more to the anatomy scan than that. "At this point in pregnancy, although the fetal organs are still immature, they are all formed, including all the inflow and outflow tracts of the heart -- the vena cava, aorta, and pulmonary arteries," says Bart Putterman, M.D., an ob-gyn at Texas Children's Pavilion for Women in Houston. "The purpose of the 20- to 22-week ultrasound is to look at all of the fetus's anatomy and to determine if all looks normal. Things that can't be seen in earlier scans, such as spinal cord abnormalities, brain defects, heart defects, and diaphragmatic abnormalities, can usually be seen on these scans."

This is also a time to measure your baby's growth, to ensure that nothing's amiss. "The size of the fetus as measured in the ultrasound should fall into the expected range for the gestational age," says Dr. Hakakha. A doctor may request additional testing if your child's growth is falling outside the predicted range. And if a problem is identified, specific recommendations can be made to prospective parents, who can then meet with appropriate specialists, and the birth can be planned at a large hospital with a level 3 neonatal ICU.

The 20-week ultrasound scan can also be helpful in ensuring a healthy and uneventful birth for you. "Details of the uterus, placenta, and amniotic fluid can be seen," says Dr. Hakakha. If your doctor notes anything unusual, she may make recommendations regarding your birth plan to help ensure that you and your baby stay safe.

What if the ultrasound shows a problem?

If your doctor does see a particular issue, she may recommend additional testing. And if there's a definite concern, such as a heart defect or neural tube issue, you'll be afforded the time to research treatment options and consult with pediatric experts, so you'll have everything ready to help your baby get the care he needs before he's even born.

Fortunately, for most parents, the 20-week anatomy scan is a happy experience -- where you'll try to count your baby's fingers and toes and finally determine (if you're so inclined) whether you need to settle on a boy's name or a girl's name.

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