A pregnancy ultrasound, also called an obstetric ultrasound or sonogram, is one of the most common tests used during pregnancy. It uses high-frequency sound waves to create images of the uterus, placenta, amniotic fluid, and developing baby.
Ultrasound does not use ionizing radiation like X-rays or CT scans. When performed by appropriately trained healthcare professionals for medical reasons, diagnostic ultrasound is generally considered safe during pregnancy. (U.S. Food and Drug Administration)
But when is a pregnancy ultrasound actually needed? What can it show? And how many ultrasounds should you have during pregnancy?
The answer depends on your stage of pregnancy, medical history, symptoms, and whether your healthcare provider needs additional information about your baby or your pregnancy.
What Is a Pregnancy Ultrasound?
A pregnancy ultrasound is an imaging test that uses sound waves to produce real-time images of the developing fetus and reproductive structures.
Depending on how far along you are and what your healthcare provider needs to evaluate, an ultrasound may be performed through the abdomen or, particularly during early pregnancy, with a transvaginal ultrasound.
An ultrasound can help evaluate:
- The location of the pregnancy
- Gestational age and fetal growth
- Fetal heartbeat and viability
- The number of babies
- Fetal anatomy
- Placental location
- Amniotic fluid
- The uterus and cervix
- Certain structural abnormalities
- Fetal position
- Some aspects of blood flow when Doppler ultrasound is medically indicated
The exact information obtained depends on the type of ultrasound and the stage of pregnancy.
When Is the First Pregnancy Ultrasound Needed?
There is no single ultrasound schedule that applies to every pregnancy.
Some women have an ultrasound early in the first trimester, while others may have their first routine ultrasound later. The timing depends on factors such as symptoms, pregnancy history, menstrual history, risk factors, and the information the healthcare provider needs.
Early Pregnancy Ultrasound
An ultrasound during the first trimester may be used to determine whether a pregnancy is located inside the uterus, evaluate the developing embryo or fetus, estimate gestational age, and assess viability.
A transvaginal ultrasound may provide clearer images during very early pregnancy because the uterus and pregnancy are still relatively small.
During an early ultrasound, the provider may evaluate:
- Gestational sac
- Yolk sac
- Embryo or fetus
- Crown-rump length
- Fetal cardiac activity when appropriate
- Location of the pregnancy
- Uterus and surrounding pelvic structures
These findings can help determine how far along the pregnancy is and whether additional evaluation is necessary. (www.aium.org)
Ultrasound During the First Trimester
A first-trimester ultrasound may be particularly useful when there is uncertainty about the pregnancy dates or when a woman has symptoms that require evaluation.
For example, a provider may recommend an early ultrasound because of:
- Vaginal bleeding
- Pelvic or abdominal pain
- Uncertain last menstrual period
- Previous pregnancy complications
- Suspected ectopic pregnancy
- Pregnancy after fertility treatment
- Suspected multiple pregnancy
- Other clinical concerns
A detailed ultrasound between approximately 12 and 14 weeks may also be recommended in certain situations, particularly when there is an increased risk of fetal or placental abnormalities. (www.aium.org)
What Does a Second-Trimester Ultrasound Show?
One of the most important ultrasound examinations during pregnancy is the detailed fetal anatomy ultrasound, often performed during the second trimester.
This examination provides a more extensive evaluation of the developing baby’s anatomy.
Depending on the examination and gestational age, the ultrasound may evaluate:
- Brain and skull structures
- Face
- Spine
- Heart
- Chest
- Abdomen
- Stomach
- Kidneys
- Bladder
- Arms and legs
- Placenta
- Amniotic fluid
- Fetal growth
- Cervix and uterus when indicated
Measurements such as head circumference, abdominal circumference, femur length, and other biometric parameters may be used to assess fetal growth and help estimate fetal size. (www.aium.org)
This examination is sometimes called the anatomy scan, anatomical survey, or 20-week ultrasound, although the exact timing can vary.
Can an Ultrasound Detect Birth Defects?
Ultrasound can identify some structural abnormalities during pregnancy, but it cannot detect every birth defect or genetic condition.
The ability to identify a problem depends on several factors, including:
- Gestational age
- The type of ultrasound
- The baby’s position
- Maternal body characteristics
- The quality of the images
- The type of condition being evaluated
- The experience of the person performing and interpreting the examination
A normal ultrasound is reassuring, but it does not guarantee that a baby has no medical or genetic conditions.
If an ultrasound identifies a possible abnormality, additional imaging, genetic testing, or consultation with a maternal-fetal medicine specialist may sometimes be recommended.
What Does a Third-Trimester Ultrasound Show?
Not every pregnant woman needs multiple routine ultrasounds during the third trimester.
However, your healthcare provider may recommend additional imaging when there is a clinical reason to monitor the pregnancy.
A third-trimester ultrasound may evaluate:
- Fetal growth
- Fetal position
- Placental location
- Amniotic fluid
- Fetal anatomy that needs follow-up
- Cervical or uterine findings when indicated
- Certain aspects of fetal well-being
- Blood flow when Doppler studies are medically appropriate
Additional ultrasounds may be considered when there are concerns about fetal growth, placental function, amniotic fluid, multiple pregnancy, maternal medical conditions, or other pregnancy complications.
Why Would a Doctor Recommend More Than One Ultrasound?
Some pregnancies require closer monitoring than others.
Additional pregnancy ultrasounds may be recommended when there is:
- A high-risk pregnancy
- A suspected growth problem
- Multiple pregnancy
- Vaginal bleeding
- Abdominal or pelvic pain
- Abnormal findings on a previous ultrasound
- Placental concerns
- Abnormal amniotic fluid levels
- Certain maternal medical conditions
- Previous pregnancy complications
- Uncertain pregnancy dates
- A need to monitor a previously identified condition
A limited ultrasound may also be used to answer a specific clinical question rather than provide a complete fetal anatomical examination. (www.aium.org)
What Is a Transvaginal Ultrasound?
A transvaginal ultrasound uses a specially designed ultrasound probe that is gently inserted into the vagina.
It is commonly useful during early pregnancy because the probe can provide detailed images of the uterus and developing pregnancy when the structures are still very small.
Your healthcare provider may recommend a transvaginal ultrasound to evaluate:
- Early pregnancy
- Pregnancy location
- Vaginal bleeding
- Pelvic pain
- The cervix
- Early pregnancy development
- Certain abnormalities involving the uterus or ovaries
Your provider can explain why this approach is being recommended and what information the examination is intended to obtain.
What Is a Transabdominal Ultrasound?
A transabdominal ultrasound is performed by moving an ultrasound transducer over the abdomen.
It is commonly used as pregnancy progresses because the uterus and fetus become larger and can be visualized through the abdominal wall.
During the examination, ultrasound gel is applied to the skin to help transmit sound waves and produce images.
Depending on the stage of pregnancy and the purpose of the examination, a transabdominal ultrasound may be combined with a transvaginal examination.
Is Pregnancy Ultrasound Safe?
Diagnostic ultrasound does not use ionizing radiation, and it has been widely used during pregnancy.
The FDA states that ultrasound has an excellent safety record when used appropriately, but ultrasound energy can produce biological effects, including slight tissue heating. For this reason, medical organizations recommend using ultrasound prudently and only when medically appropriate, with exposure kept as low as reasonably achievable. (U.S. Food and Drug Administration)
This is one reason medical pregnancy ultrasounds should be performed by appropriately trained professionals.
What About 3D and 4D Ultrasounds?
3D ultrasound can produce three-dimensional images, while 4D ultrasound adds movement to those images.
These technologies can provide additional visualization in certain medical situations. However, ultrasound should not be performed simply for prolonged keepsake imaging without a medical indication.
The FDA and AIUM discourage nonmedical fetal ultrasound examinations performed solely to obtain keepsake images or videos. (U.S. Food and Drug Administration)
Can an Ultrasound Tell the Baby’s Sex?
Depending on the baby’s position and gestational age, an ultrasound may sometimes provide information about fetal sex.
However, determining fetal sex is not the primary medical purpose of an obstetric ultrasound. The main purpose is to evaluate the pregnancy and assess fetal development and maternal structures.
An ultrasound also should not be considered a substitute for genetic screening or diagnostic testing when those tests are recommended.
Does Every Pregnancy Need the Same Number of Ultrasounds?
No.
Some pregnancies may require only routine ultrasound examinations, while others require several scans to monitor specific concerns.
The number and timing of pregnancy ultrasounds can depend on:
- Your medical history
- Your pregnancy history
- Gestational age
- Symptoms
- Risk factors
- Findings from previous examinations
- Fetal growth
- Placental or amniotic fluid concerns
- Whether you are carrying more than one baby
Your obstetric provider can determine which examinations are appropriate for your individual pregnancy.
What Happens During a Pregnancy Ultrasound?
A typical ultrasound appointment may begin with questions about your pregnancy and medical history.
For a transabdominal ultrasound, you will generally lie on an examination table while the provider applies ultrasound gel to your abdomen and moves the transducer over the area.
For a transvaginal ultrasound, the provider uses a covered ultrasound probe designed for internal imaging.
The examination is generally noninvasive, although a transvaginal ultrasound can cause some pressure or mild discomfort.
The ultrasound images are reviewed to obtain the information needed for your pregnancy care.
When Should You Contact Your Doctor Before Your Scheduled Ultrasound?
You should contact your pregnancy care provider if you develop symptoms that could require evaluation before your next scheduled appointment.
These can include:
- Vaginal bleeding
- Significant abdominal or pelvic pain
- Severe or persistent cramping
- Leakage of fluid
- Fever
- Severe headache or vision changes
- Sudden swelling
- Decreased fetal movement later in pregnancy
- Severe dizziness or fainting
- Other symptoms that concern you
Some symptoms during pregnancy require urgent medical evaluation rather than waiting for a scheduled ultrasound.
What If an Ultrasound Shows Something Abnormal?
An ultrasound finding does not automatically mean that there is a serious problem.
Sometimes an image may be unclear because of fetal position, gestational age, or other technical factors. Your provider may recommend a repeat ultrasound to obtain better images or monitor a finding over time.
If a potential abnormality is identified, additional testing may be recommended.
Depending on the situation, this could include:
- A more detailed ultrasound
- Repeat ultrasound
- Genetic screening
- Diagnostic genetic testing
- Fetal echocardiography
- Additional maternal blood tests
- Consultation with a maternal-fetal medicine specialist
Your healthcare provider can explain what the finding means and what the next step should be.
Pregnancy Ultrasound FAQs
When is the first ultrasound usually done?
The timing varies. Some women have an ultrasound during the first trimester, while others have their first routine examination later. An earlier scan may be recommended when there are symptoms, uncertain dates, fertility treatment, or other clinical reasons.
Is an ultrasound necessary during every pregnancy?
Ultrasound is an important part of pregnancy care, but the exact number and timing of examinations depend on the individual pregnancy and clinical circumstances.
Can an ultrasound confirm pregnancy?
Ultrasound can confirm an intrauterine pregnancy once the pregnancy is far enough along for the relevant structures to be visualized. Very early in pregnancy, blood or urine pregnancy testing may detect pregnancy before ultrasound can provide definitive findings.
Can an ultrasound determine how far pregnant I am?
Yes. Ultrasound measurements can be used to estimate gestational age, particularly early in pregnancy when certain measurements are useful for pregnancy dating.
Can an ultrasound detect twins?
Yes. Ultrasound can identify multiple pregnancies and provide information about the number of fetuses and, when appropriate, features of the placentas and amniotic sacs.
Can an ultrasound show the baby’s heartbeat?
Cardiac activity may be visualized during an early pregnancy ultrasound once the pregnancy has developed sufficiently. The timing at which it can be detected varies.
Is a 20-week ultrasound mandatory?
The detailed anatomy ultrasound is an important component of prenatal evaluation, but recommendations can vary depending on the pregnancy and healthcare setting. Your provider can explain which ultrasound examinations are appropriate for you.
Are pregnancy ultrasounds painful?
Most ultrasounds are not painful. A transvaginal ultrasound may cause temporary pressure or mild discomfort, while a transabdominal ultrasound generally causes little discomfort.
When Should You Schedule a Pregnancy Ultrasound?
If you are pregnant or think you may be pregnant, your healthcare provider can help determine when an ultrasound is appropriate based on your gestational age, symptoms, medical history, and pregnancy risk factors.
If you are experiencing pain, bleeding, or another concerning symptom, you may need evaluation sooner rather than waiting for a routine prenatal appointment.
For women in Eagle Pass, Texas, Southwestern Women’s Clinic can be a resource for discussing pregnancy concerns and determining what type of prenatal evaluation may be appropriate.
Pregnancy Care in Eagle Pass, Texas
Understanding when a pregnancy ultrasound is needed can make prenatal care less confusing. Ultrasound can provide valuable information about fetal development, pregnancy dating, fetal anatomy, placental location, and other aspects of pregnancy.
However, not every pregnancy requires the same ultrasound schedule. The appropriate timing and type of examination should be determined according to your individual health and pregnancy needs.
If you are looking for women’s healthcare in Eagle Pass, Texas, contact Southwestern Women’s Clinic to discuss your pregnancy, symptoms, and prenatal care needs.
Medical Disclaimer
This article is intended for general educational purposes and does not replace medical advice, diagnosis, or treatment from a qualified healthcare professional. Pregnancy care is individualized. If you are pregnant and experiencing severe pain, heavy bleeding, fainting, decreased fetal movement, or other concerning symptoms, seek prompt medical attention.
