Your 12-week ultrasound is meant to assess your baby’s development at the end of the first trimester of your pregnancy. At week 12, the fetus’s organs and body systems are formed, and you may actually be seeing your baby for the first time.
Ultrasound (often called sonography, since it relies on sound waves) is a non-invasive, low-risk imaging method that can be used to establish your due date and confirm the number of developing fetuses. A healthcare provider may screen for Down syndrome or rule out an ectopic pregnancy.
This article talks about what to expect at your 12-week ultrasound, its importance, and why there are relatively no risks to you or your child. It also explains the types of ultrasound procedures, questions to ask, and ways to prepare for your appointment.
A 12-week ultrasound is done in the first trimester, while you’re still in an early stage of pregnancy, to get a view of the baby’s overall development. Ultrasounds at 12 weeks are common but not standard, because not enough development has taken place at this stage for your healthcare provider to visualize your baby’s limbs and organs in detail.
However, a 12-week ultrasound may be used to:
- Estimate your gestational age and due date
- Screen for certain disorders, such as Down syndrome or cystic hygroma
- Count the number of fetuses
- Check your baby’s heart rate
- Rule out an ectopic pregnancy (when a fertilized egg implants outside of the uterus)
While most women usually have two ultrasounds—one around 12 weeks gestation and one around 20 weeks—your healthcare provider may perform just one. If only one ultrasound is performed, it will take place at around 20 weeks in order to:
- Check the fetal position, movement, and heart rate
- Estimate your baby’s size and weight
- Check the amount of amniotic fluid in the uterus
- Find the location of the placenta
- Confirm the number of fetuses
- Assess for abnormalities or birth defects
In some cases, certain conditions like placental insufficiency (leading to poor oxygen and nutrient delivery to the fetus) may be identified early and better managed throughout the pregnancy. This can inform care decisions and planning, such as with a cesarean section delivery.
Most miscarriages happen within the first 12 weeks of pregnancy, often due to genetic abnormalities. An ultrasound may be used to confirm a miscarriage. It also may identify an emerging condition that can present a later miscarriage risk, such as a placental problem.
Screening for Down Syndrome
The screening test for Down syndrome and two chromosomal disorders, trisomy 13 and trisomy 18, used at this stage of pregnancy is called a combined test. It involves a blood test and a test to measure fluid at the back of the baby’s neck (nuchal translucency) with an ultrasound scan.
However, combined screening is not a diagnostic test, which means it cannot tell you whether your baby has Down syndrome, trisomy 13, or trisomy 18. Instead, the screening provides a probability that the baby might have one of these genetic disorders.
The probability, or chance, is based on three criteria:
- Your age
- Information obtained on an ultrasound
- Bloodwork results
The screening results can either alert you and your healthcare provider to an increased risk for one of these chromosomal disorders, or reassure you that your baby is at a lower risk for them.
A positive result that shows an increased risk does not mean that your baby has a problem, and a negative or normal result (one that shows a decreased risk) does not mean that the baby will not have a chromosomal abnormality.
12-Week Screening Test Accuracy
The first-trimester screening’s detection rate is about 96% accurate for Down syndrome and is somewhat higher for pregnancies with trisomy 13 or trisomy 18. A nuchal translucency ultrasound can be done without bloodwork, but the detection rate is lower at 70%.
What Happens During the 12-Week Ultrasound?
Your healthcare provider will likely perform a transabdominal ultrasound, which transmits waves through your abdomen. In some cases, a transvaginal ultrasound may be performed to capture more direct or detailed images. A scan usually takes 20 to 30 minutes to complete.
During a transabdominal ultrasound, you will be asked to lie down on an exam table—either in a procedure room or your healthcare provider’s office—with your abdomen exposed from your ribs to your hips. You may be asked to arrive at your appointment with a full bladder, which will create a window to the womb area.
When the test is ready to begin, your healthcare provider will:
- Apply an ultrasound gel to help conduct the sound waves to your skin. This will help improve the quality of the images produced by the ultrasound.
- Move a handheld ultrasound transducer back and forth across your abdomen using a small amount of pressure. This should not be painful, although you may experience some discomfort related to positioning.
They may pause over certain areas of your abdomen to capture specific images or measurements. Measurements will be taken from different sections of the baby’s body and your uterus. A short recording may be captured of your baby’s heart movement.
You may be given some initial information about your baby at the time of your ultrasound exam, but a detailed report will likely come afterwards, once it is examined by a radiologist. Your healthcare provider will then discuss the results with you.
During a transvaginal ultrasound, you will be asked to undress from the waist down, or you may even be asked to remove your clothing and wear a hospital gown. Unlike the transabdominal ultrasound, you will be asked to empty your bladder before the test begins.
When you are ready to begin the test, you will be asked to lie down on an exam table with your feet in stirrups, much like you would for a pelvic exam.
A wand-shaped transducer covered in a protective sheath will be inserted through the vagina for an internal view of the uterus. This should not be painful, but you may feel discomfort as you would during a pelvic exam.
Questions to Ask Your Provider
Your healthcare provider will gather a great deal of information from the 12-week (or later 20-week) ultrasound images. Be sure to ask about:
You’ll also want to discuss the risk of birth defects due to your health or genetic history, or what steps will be needed to protect your health in the case of a high-risk pregnancy.
Fetal Sex Markers and 12-Week Ultrasounds
Ultrasound is still the most common method to learn the sex of a developing fetus, and it is about 79% accurate at 12 weeks. However, the 12-week ultrasound doesn’t approach the same accuracy as non-invasive prenatal testing (NIPT) until about 14 weeks. The NIPT requires only a blood sample from the pregnant person and is often used to identify sex-specific risks to the fetus like Duchenne muscular dystrophy.
While the above describes a standard 12-week or first-trimester ultrasound, there may be reasons for your healthcare provider to request additional scans.
If you experience bleeding or other concerning symptoms, your healthcare provider may order a limited ultrasound to quickly check for a specific issue. This could occur at any point during your pregnancy.
You may also be asked to undergo a specialized ultrasound or have more regular scans performed. These ultrasound scans are conducted in the same manner as the 12-week ultrasound but may examine the fetus in closer detail, with three-dimensional imaging.
In most cases, you can expect an additional routine ultrasound at 18 to 22 weeks.
Potential Risks to Receiving an Ultrasound
Ultrasound relies on sound waves rather than radiation, which makes it safer than X-rays and other types of imaging. The Food & Drug Administration, along with professional organizations, confirm its benefits and safety for use during pregnancy. That said, ultrasound for non-medical purposes (like ‘keepsake’ videos) is discouraged.
It’s common for a healthcare provider to order a 12-week ultrasound. This routine screening is usually done with a transducer wand placed at the abdomen, to generate images based on sound waves that are used to assess the developing fetus.
The images can reveal the gestational age of the fetus and identify if there’s more than one. It can be used to screen for Down syndrome, or for low birth weight or placenta problems that can make the pregnancy high-risk. Speak with your healthcare provider if you have questions about your ultrasound or your results.