What Happens During a 20-Week Anatomy Scan

Pregnancies are filled with major milestones. From the positive pregnancy test, the first prenatal appointment, and the end of the first trimester to last day of morning sickness and the nausea that can come along with it. Prenatal appointments also are filled with milestones.

During some prenatal appointments, you’ll have a few unpleasant tasks you’ll need to do, such as bloodwork or glucose screenings. At other appointments, you may get to hear your baby’s heartbeat. No matter the appointment, though, it’s important that you know what to expect at a prenatal care checkup.

One of the biggest prenatal checkups is the 20-week anatomy scan. This is around the halfway mark of the pregnancy and it is where you get to find out more about your baby’s physical development.

What Is a 20-Week Anatomy Scan?

Halfway through the pregnancy! This can be both an exciting and nerve-wracking time for expectant parents. The 20-week anatomy scan can help fill you in on some questions you might have about your baby’s development.

The 20-week anatomy scan is an ultrasound performed by a sonographer to look at the baby’s bones and organs to measure proper growth. The sonographer, a health care professional who specializes in the use of ultrasonic imaging devices, also will look for specific conditions or abnormalities.

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What Is Identified During a 20-Week Anatomy Scan?

The 20-week anatomy scan looks at the baby’s bones (especially their arms, legs, feet, and hands), face, brain, heart, spinal cord, kidneys, stomach, bladder, and genitals.

The sonographer will estimate your baby’s weight and length at the 20-week anatomy scan. According to the American Pregnancy Association, babies should measure about 7-3/4 inches long and weigh approximately 9 ounces at this point in the pregnancy.

In addition to your baby’s growth, the sonographer also will:

  • Measure blood flow in the umbilical cord where it attaches to the placenta.
  • Measure the amount of amniotic fluid.
  • Check for placenta previa, which, according to March of Dimes, happens when the placenta lies low in the uterus and covers all or part of the opening to the vagina.
  • Examine your ovaries, cervix, and uterus.

What Abnormalities Can Be Identified?

In addition to weight and length, the sonographer is looking at growth in:

  • Arms and legs: A baby’s arms, legs, fingers, and toes should be fully formed.
  • Spine: A normally developing baby should have a fully formed spine with all bones aligned. The 20-week anatomy scan can pick up spina bifida, which also may be detected by other anatomy scans sometimes as early as the end of the first trimester.
  • Face (cleft lip/cleft palate): Also called orofacial clefts, cleft lip and cleft palate occur when a baby’s lip or mouth do not form properly during pregnancy. The lip forms between the fourth and seventh week of pregnancy and the palate is formed between the sixth and ninth week of pregnancy. According to the Centers for Disease Control (CDC), in the United States, about 1 in every 1,600 babies is born with cleft lip with cleft palate; about 1 in every 2,800 babies is born with cleft lip without cleft palate; and about 1 in every 1,700 babies is born with cleft palate.
  • Brain: Although rare, doctors will check for conditions such as anencephaly, a birth defect in which a baby is born without parts of the brain and skull.
  • Kidneys: At 20 weeks, your baby should have two kidneys. Both kidneys will be checked to ensure they are developing properly and do not have bilateral renal agenesis.
  • Heart: Your baby’s heart rate should range from 120 to 160 beats per minute, and all four chambers should be developed.
  • Stomach: The scan will check to ensure your baby’s stomach is developing normally and look for gastroschisis, an abdominal wall defect.

Can I Find Out the Sex of My Baby?

While some parents like to wait until delivery to find out whether they are having a boy or a girl, others want to know as soon as possible. For those who just can’t wait, this appointment can be an exciting one.

Ultrasounds can determine the sex of a baby as early as 14 weeks, but the 20-week anatomy scan is a common time for the parents-to-be to find out, if they choose to do so.

For those with less patience, noninvasive prenatal testing is available at the 10-week mark, which uses a blood test to determine the baby’s sex, among other things.

When Will I Receive the Results of the Scan?

The sonographer will be able to tell you the results of the scan in real time while they are performing the ultrasound. Don’t fret if they are not extremely talkative, though, as they are working to carefully take and label each image of your little one! Even before they are born, babies can be stubborn and the sonographer might have to get some creative angles, or even do some tricks to get the baby to move to a new position.

While most scans will show the baby is developing as expected, there will be times where follow-ups are needed. In this case, your doctor or midwife will consult you and go over additional information.

How Do I Prepare For the 20-Week Anatomy Scan?

For the most part, there is nothing special you need to do in advance of your anatomy scan. Because this is one of the longer prenatal appointments, make sure you are wearing comfortable clothing, and don’t be hesitant to ask for a break if needed.

If you would like to bring someone along, be sure to ask your provider about their policies regarding bringing your partner or another guest.

The Best Care for You and Your Baby

At UPMC Magee-Womens Hospital, we understand that welcoming a new baby into the world is a special experience. Whether you’re looking for classes to help you prepare for parenthood, or you’re a new mom looking for support, we have caring, expert providers and a host of resources and information to help you.



















About UPMC Magee-Womens

Built upon our flagship, UPMC Magee-Womens Hospital in Pittsburgh, and its century-plus history of providing high-quality medical care for people at all stages of life, UPMC Magee-Womens is nationally renowned for its outstanding care for women and their families.

Our Magee-Womens network – from women’s imaging centers and specialty care to outpatient and hospital-based services – provides care throughout Pennsylvania, so the help you need is always close to home. More than 25,000 babies are born at our network hospitals each year, with 10,000 of those babies born at UPMC Magee in Pittsburgh, home to one of the largest NICUs in the country. The Department of Health and Human Services recognizes Magee in Pittsburgh as a National Center of Excellence in Women’s Health; U.S. News & World Report ranks Magee nationally in gynecology. The Magee-Womens Research Institute was the first and is the largest research institute in the U.S. devoted exclusively to women’s health and reproductive biology, with locations in Pittsburgh and Erie.