Most people with a low-risk pregnancy have two routine ultrasounds: one in the first trimester and one around 20 weeks. That said, the actual number you experience can range from one to a dozen or more, depending on your health, your baby’s growth, and your provider’s approach.
The Two Standard Scans
The first ultrasound typically happens between 8 and 12 weeks. Its main job is to confirm the pregnancy is in the right location, check for a heartbeat, and measure the embryo to establish your due date. First-trimester measurement is the most accurate method for dating a pregnancy, and getting that date right early has real downstream effects. It helps your provider time lab work and screenings correctly, judge whether your baby is growing on track later on, and avoid unnecessary inductions for a pregnancy mistakenly thought to be overdue. A large review found that routine early ultrasound reduced the rate of postterm inductions for exactly this reason.
The second standard scan is the anatomy survey, usually done between 18 and 22 weeks. This is the big one. A sonographer takes detailed measurements and images of the baby’s heart, brain, spine, kidneys, limbs, face, lungs, stomach, and intestines. They also record the heart rate, check blood flow through the umbilical cord, note the placenta’s position, and measure the amount of amniotic fluid surrounding the baby. If you want to learn the sex, this is usually the appointment where that happens. The anatomy scan can take 30 to 45 minutes because there’s a long checklist to get through, and a squirmy baby sometimes makes certain angles hard to capture.
Scans That Fall Between the Two
Some providers offer or recommend a nuchal translucency scan between 11 weeks and 13 weeks, 6 days. This measures a small pocket of fluid at the back of the baby’s neck, and the measurement is combined with blood work to screen for chromosomal conditions like Down syndrome. Not every practice includes this scan as standard, so it may or may not be part of your schedule. The timing window is narrow, so if you want it, your provider needs to schedule it before 14 weeks.
Between 15 and 24 weeks, some providers also screen for a short cervix using a transvaginal ultrasound, particularly if you have a history of preterm birth. This is a quick scan focused on a single measurement and is separate from the anatomy survey.
Why Some Pregnancies Need More
A low-risk pregnancy with no complications may not require any ultrasound beyond the anatomy scan. But several common situations add scans to the schedule:
- Uncertain dates or early concerns. If you’re unsure of your last period, have irregular cycles, or experience bleeding or cramping, your provider will likely order an early ultrasound (sometimes before 8 weeks) to confirm viability and location.
- Growth concerns. If your provider measures your belly at a prenatal visit and it seems smaller or larger than expected for your gestational age, a growth scan in the third trimester can check whether the baby’s size is on track. If a problem is found, growth scans may repeat every two to four weeks.
- Gestational diabetes, high blood pressure, or other complications. These conditions increase the need for monitoring. For some people, a high-risk pregnancy means only an extra scan or two. For others with more serious complications, ultrasounds may happen weekly in the final weeks.
- Twins or higher-order multiples. Multiple pregnancies are monitored more frequently because growth discrepancies between babies can develop quickly.
- Advanced maternal age or prior pregnancy loss. Providers often recommend additional surveillance in these situations, including periodic checks of fetal well-being.
Specialized Ultrasounds Later in Pregnancy
If your provider has concerns about the baby’s well-being in the third trimester, they may order a biophysical profile. This combines an ultrasound with fetal heart rate monitoring and evaluates five specific areas: heart rate, breathing movements, body movements, muscle tone, and amniotic fluid volume. Each area scores 0 or 2 points, for a total possible score of 10. A high score is reassuring; a low score may lead to closer monitoring or, depending on how far along you are, a conversation about delivery timing. This type of scan is not routine for low-risk pregnancies, but it’s common enough that many people encounter it at least once.
Transvaginal vs. Transabdominal
Most ultrasounds from the second trimester onward use the familiar gel-on-the-belly (transabdominal) approach. Early in pregnancy, though, your provider may use a transvaginal probe instead. This gives a much clearer picture when the embryo is tiny. Transabdominal imaging can reliably detect a gestational sac early on, but it’s significantly less sensitive at picking up the embryonic pole, which is the first visible sign of the developing embryo. That gap widens for people with a higher BMI. A transvaginal scan in the first trimester is not a sign that something is wrong. It’s simply a better tool for the job at that stage.
Keepsake and 3D/4D Scans
Commercial studios offer 3D and 4D ultrasounds as a way to get detailed photos or videos of your baby’s face before birth. The FDA and major medical organizations discourage these non-medical scans because they involve prolonged ultrasound exposure without a diagnostic purpose. Diagnostic ultrasound follows what’s called the ALARA principle: using the lowest amount of energy for the shortest time needed to get medically useful images. When a trained sonographer captures a cute photo during a scheduled medical scan, that’s fine because it doesn’t add extra exposure. A separate session at a boutique studio, run by someone who may not have clinical training, is a different situation. The risks of any single ultrasound session are very low, but unnecessary exposure offers no medical benefit to weigh against even a small theoretical risk.
What a Typical Schedule Looks Like
Putting it all together, here’s what most people can expect:
- 8 to 12 weeks: Dating and viability scan
- 11 to 14 weeks (optional): Nuchal translucency screening
- 18 to 22 weeks: Anatomy survey
- Third trimester (if needed): Growth scans or biophysical profiles
That gives most low-risk pregnancies two or three ultrasounds total. If complications arise, the number can climb to five, eight, or more. Each additional scan is ordered because it provides information your provider needs to keep you and your baby safe, not because more ultrasounds are inherently better. If you’re ever unsure why a scan is being recommended, asking your provider what they’re looking for is a reasonable question with a straightforward answer.