Most pregnant women have at least two ultrasounds: one in the first trimester and one around 20 weeks. In a low-risk pregnancy, ACOG recommends a minimum of one standard ultrasound at 18 to 22 weeks, though most providers also perform an early scan to confirm the due date. High-risk pregnancies can involve significantly more, sometimes weekly in the final trimester.
The Standard Two-Scan Schedule
For a straightforward, low-risk pregnancy, you can expect two routine ultrasounds. The first typically happens in the first trimester, and the second is the detailed anatomy scan in the middle of your pregnancy. Some providers only schedule the anatomy scan if the pregnancy is progressing normally and dates are already certain from other methods, which is why guidelines say “at least one.”
First Trimester: The Dating Scan
This scan usually takes place between 7 and 13 weeks. Its main purpose is to establish your due date by measuring the length of the embryo from head to rump. That measurement is the single most accurate way to determine gestational age, with a margin of error of only five to seven days. The technician will also confirm a heartbeat, check whether you’re carrying more than one baby, and rule out an ectopic pregnancy.
A first trimester scan isn’t considered mandatory for every pregnancy. If your menstrual dates are reliable and your provider has no concerns, this scan may be skipped. In practice, though, most clinics in the U.S. include it as a standard part of prenatal care.
The 20-Week Anatomy Scan
This is the big one. Performed between 18 and 22 weeks, it’s a thorough head-to-toe check of the baby’s development. The sonographer will take measurements and images of the heart, brain, spine, kidneys, bladder, lungs, stomach, intestines, limbs, and even individual fingers and toes. They’ll also look at the baby’s face, checking the lips, nose, chin, and eyes.
Beyond the baby itself, the scan evaluates the placenta’s position, blood flow through the umbilical cord, the amount of amniotic fluid, and the length of your cervix. This is also when many parents learn the sex, though that’s optional. The entire appointment usually runs 30 to 45 minutes because there’s a long checklist of structures to document. If the baby is in an awkward position, you may be asked to walk around and come back so the sonographer can get the remaining views.
When You’ll Need More Scans
Several conditions can push the total number well above two. Common reasons for additional ultrasounds include:
- High blood pressure or preeclampsia, which requires monitoring of blood flow to the baby
- Gestational or pre-existing diabetes, because uncontrolled blood sugar can affect the baby’s growth rate
- Carrying twins or multiples, which raises the risk of complications for both parent and babies
- A size discrepancy, where the uterus measures larger or smaller than expected for the gestational age
- Pregnancies conceived through IVF or other assisted reproductive technologies, which carry a higher baseline risk
- Thyroid disease, heart conditions, or blood disorders in the parent
In these situations, your provider may order growth scans in the third trimester to track the baby’s weight gain. If there’s a specific concern about the baby’s well-being, you might also have a biophysical profile, which is a specialized ultrasound that scores five things: heart rate, breathing movements, body movements, muscle tone, and amniotic fluid levels. These are sometimes repeated weekly or even twice a week in the final stretch of pregnancy.
Third Trimester Scans Aren’t Routine
If your pregnancy is progressing normally, you won’t automatically get a third trimester ultrasound. A late scan is typically ordered only when something flags a concern, like a gap between your belly measurement and the expected size for your stage of pregnancy. Some countries include a routine growth scan around 32 to 36 weeks as part of standard care, but in the U.S. it remains indicated rather than universal for low-risk pregnancies.
Keepsake and 3D/4D Scans
Commercial ultrasound studios offer 3D and 4D imaging sessions purely for keepsake photos and videos. Both the FDA and the American Institute of Ultrasound in Medicine discourage this practice. While diagnostic ultrasound is considered safe when performed by trained professionals for a medical purpose, the concern is unnecessary and prolonged exposure to ultrasound energy from untrained operators. If you want a 3D image, a reasonable approach is to ask during one of your medically indicated appointments, since many providers will capture a keepsake photo without adding extra exposure time.
Are Multiple Scans Safe?
Diagnostic ultrasound does not use radiation. It works by bouncing sound waves off tissue and converting the echoes into an image. There is no established cumulative dose limit in the way there is for X-rays. That said, safety guidelines follow the ALARA principle: as low as reasonably achievable. Technicians are trained to keep the power output low and the scan time as short as needed to get the clinical information.
Specific recommendations include starting every scan with a thermal index of 0.7 or below and avoiding routine use of Doppler modes, which produce higher acoustic output. In practical terms, this means medically indicated ultrasounds at the intervals your provider recommends carry minimal risk. What you want to avoid is frequent, prolonged, non-medical scanning with no clinical purpose.
A Realistic Count by Trimester
For a low-risk pregnancy, two to three scans total is typical: a dating scan, the anatomy scan, and possibly one more if your provider wants to check something specific. For a high-risk pregnancy, the total can easily reach five to ten or more, depending on the condition being monitored. Women with complications in the final weeks may have ultrasounds at every prenatal visit.
Your individual number will depend on your health history, how the pregnancy is progressing, and your provider’s practice patterns. More scans don’t necessarily mean something is wrong. They often just mean your care team wants a closer look to keep things on track.