When and Why Pregnancy Ultrasounds Are Done

Most people only need a couple of ultrasounds during pregnancy, but in certain situations, you may need more. Read on to learn more about when and why you may need these important prenatal scans.

Most pregnant people have a couple of ultrasounds throughout their prenatal care, but some have them more frequently. Uncomplicated pregnancies typically have fewer ultrasounds than high-risk pregnancies, but how many you receive over the course of your pregnancy will vary. Your preference, provider's standard protocol, ultrasound machine access, medical history, and complications may influence how many ultrasounds you receive.

During a pregnancy ultrasound, your health care provider or a skilled technician uses a plastic transducer to transmit high-frequency sound waves through your uterus. These sound waves send signals back to a machine that converts them into images of your baby.

According to the American College of Obstetricians and Gynecologists (ACOG), health care providers may use ultrasounds for:

  • Monitoring your baby's growth and development
  • Detecting congenital anomalies
  • Guiding an amniocentesis
  • Helping predict your due date
  • Determining whether you're carrying multiples
  • Showing the position of your placenta
  • Estimating your baby's size
  • Measuring amniotic fluid
  • Revealing your baby's genitals

Read on for a breakdown of the most common types of pregnancy ultrasounds and when you should expect them.

First Trimester Ultrasounds

Not everyone receives a first-trimester ultrasound during pregnancy, but sometimes a health care provider may use them for determining viability, dating the pregnancy, or if there are suspected complications.

Early pregnancy (6–8 weeks)

Your first ultrasound, also known as a fetal ultrasound or sonogram, could occur as early as six to eight weeks into your pregnancy. In addition to a pregnancy test, some health care providers use ultrasounds to confirm pregnancy.

According to the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG), early pregnancy ultrasounds can:

  • Confirm viability
  • Establish gestational age
  • Determine the number of fetuses
  • Determine if multiples share a placenta and amniotic sac

But not everyone will get this early scan. ISUOG does not recommend routine early pregnancy ultrasounds unless there is a clinical indication of a complication. So, for example, some health care providers will only conduct early ultrasounds for certain high-risk pregnancy conditions like bleeding, abdominal pain, or to rule out ectopic pregnancy, congenital disorders, or miscarriage.

In early pregnancy, ultrasound is usually done transvaginally, which gives the clearest picture of your uterus and embryo at this early stage. In this case, the provider will place a thin wand-like transducer probe—which transmits high-frequency sound waves through your uterus—into your vagina. The sound waves bounce off the fetus and send signals back to a machine that converts these reflections into a black-and-white image of your uterus.

Although the heart structures aren't yet fully developed at six weeks gestation, it's possible to see the electrical impulses of their developing heart (sometimes referred to as embryonic cardiac activity).

Nuchal translucency ultrasound (10–13 Weeks)

A nuchal translucency (NT) ultrasound occurs around weeks 10 to 13 of pregnancy. According to ACOG, this ultrasound measures the space at the back of a fetus' neck. Abnormal measurements can indicate Down syndrome and other congenital disabilities of the heart, abdomen, and skeleton. In addition to an abdominal ultrasound, an NT screening includes measuring hormones and proteins with a blood test.

This test is optional for everyone who is pregnant. Sometimes, people choose to have this ultrasound to alleviate concerns about their baby's health. Other times, your health care provider might recommend it if you are at risk of complications or have a family history of congenital disorders.

In addition to screening for anomalies, this ultrasound can offer the same information as an earlier scan, including an estimated due date, your baby's "crown-rump length" (measurement from head to bottom), the number of babies in the womb, and fetal cardiac activity.

Second Trimester Ultrasound

The second trimester is the most common time for a routine prenatal ultrasound. The anatomy scan, a thorough scan of your baby's developing body and organs, is offered to every pregnant person.

Anatomy scan (18–22 Weeks)

According to ACOG, this detailed pregnancy ultrasound generally happens between weeks 18 and 22 in the second trimester. It's the most thorough check-up your baby will have before they're born.

During the anatomy scan, also called a level II ultrasound, the health care provider will check your baby's heart rate and look for abnormalities in their brain, heart, kidneys, and liver, says Jane Chueh, M.D., director of prenatal diagnosis and therapy at Lucile Children's Hospital Stanford, in Palo Alto, California.

They'll also count your baby's fingers and toes, examine the placenta, and measure the amniotic fluid level. And they'll probably be able to see your baby's genitals to guess your baby's sex, although it's not a slam dunk. If you don't want to know about your baby's genitalia, be sure to inform the technician ahead of time.

What Is Gender?

Even though people often look forward to this pregnancy ultrasound to learn their baby's gender, it's important to note that gender is a personal identity that exists on a spectrum, can change over the course of a person's lifetime—and most importantly—is something that a person defines for themselves. Sex is assigned at birth based on the appearance of a baby's genitalia. While sex assigned at birth often matches a person's gender (called cisgender), sometimes, for transgender, intersex, and gender nonbinary people, it does not.

Third Trimester Ultrasound

Many parents-to-be don't need an ultrasound in the third trimester. But if your pregnancy is considered high-risk, it may be recommended.

For example, if you have high blood pressure, bleeding, low levels of amniotic fluid, preterm contractions, or are over age 35, your doctor may perform in-office, low-resolution ultrasounds during some of your third-trimester prenatal visits for reassurance, says Dr. Chueh. In addition, if an earlier scan found your placenta was near or covering the cervix (called placenta previa), you'll require additional ultrasounds to monitor its location.

Special Situation Ultrasounds

In some situations, your health care provider may recommend an ultrasound during pregnancy outside of those mentioned above. For example, these ultrasounds might be indicated if you have certain health conditions that warrant specific monitoring or if you have a procedure that uses ultrasound guidance.

Doppler ultrasound

Doppler ultrasound is a special imaging test showing blood moving through vessels. In pregnancy, a doppler ultrasound can help determine if your baby's blood is circulating properly. According to a Cochrane review, doppler ultrasound in high-risk pregnancies may reduce the risk of perinatal death and obstetric interventions.

Your health care provider may recommend fetal doppler ultrasound in the following circumstances:

  • You have diabetes
  • You have high blood pressure
  • You have heart or kidney problems
  • The placenta does not develop properly
  • Suspected fetal growth problems

Handheld fetal heartrate monitors also utilize doppler technology. Health care providers commonly use these devices to monitor your baby's heartbeat during prenatal exams and labor. While these are available over the counter, the Food and Drug Administration (FDA) advises against using them at home due to lack of oversight and unnecessary ultrasound exposure.

Guiding ultrasounds

Your health care provider may also order other pregnancy tests that require ultrasounds for guidance. These might include chorionic villus sampling (CVS) or amniocentesis, which screen the baby for congenital disorders. Fetal echocardiograms, which show the baby's heart rate and detect anomalies, also use ultrasound technology.

How Many Ultrasounds During Pregnancy Are Safe?

Ultrasound is considered safe for you and your baby when used for medical purposes. Although ultrasounds require no radiation, only a trained professional who can accurately interpret the results should perform them. Your technician should have education in obstetrical ultrasound, preferably at a center accredited by the American Institute of Ultrasound in Medicine.

Some medical practices offer 3D (high quality and lifelike) and 4D (moving picture) ultrasounds, which may help doctors detect specific fetal abnormalities and congenital disorders. However, these exams are also available at fetal portrait studios in places like shopping malls.

Experts discourage these "keepsake" ultrasounds since untrained personnel may give out inaccurate information, says Michele Hakakha, M.D., an OB-GYN in Beverly Hills and author of Expecting 411: The Insider's Guide to Pregnancy and Childbirth.

Plus, according to the FDA, although ultrasounds are safe in medical settings, they might heat tissues or produce bubbles (cavitation) during use if not performed correctly. Experts aren't sure about the long-term effects of heated tissues or cavitation, especially when not medically indicated. Therefore, the FDA advises that people use ultrasound scans judiciously—only when there is a medical need, based on a prescription, and performed by appropriately-trained health care providers.

How Much Does an Ultrasound Cost?

Ultrasounds aren't cheap; they can cost hundreds or thousands of dollars, depending on your location and health care provider. However, most health insurance plans will cover the cost of prenatal ultrasounds (at least partially) if they are for medical purposes. Always ask your health care provider and insurance company if you're unsure how much you will need to pay.

Updated by Nicole Harris
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  1. Ultrasound Exams, ACOG, 2021

  2. ISUOG Practice Guidelines: performance of first-trimester fetal ultrasound scan, Wiley’s Obstetrics and Gynaecology, 2012

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