Most pregnant women get two ultrasounds: one in the first trimester around 10 to 14 weeks and one mid-pregnancy between 18 and 22 weeks. The American College of Obstetricians and Gynecologists recommends at least one standard ultrasound during pregnancy, typically the mid-pregnancy scan. In practice, though, most providers schedule both. If your pregnancy is considered high-risk, you could have significantly more.
The Two Routine Scans
The first scan, often called a dating scan, usually happens between 10 and 14 weeks. Its main job is to confirm how far along you are, calculate your due date, check that the baby is growing in the right place, and determine whether you’re carrying more than one baby. At this stage it’s too early to see organs and limbs in detail, which is why ACOG doesn’t consider it strictly mandatory, but most OB practices include it as standard care.
The second is the anatomy scan, performed between 18 and 22 weeks. This is the big one. The sonographer will spend time looking closely at your baby’s bones, heart, brain, spinal cord, face, kidneys, and abdomen. They also check the placenta’s position and blood flow in the uterus. This scan is when many parents learn the sex, but its primary purpose is screening for structural problems. It’s the one ultrasound that virtually every provider recommends regardless of risk level.
Optional First-Trimester Screening
Between 11 and 13 weeks, your provider may offer a nuchal translucency scan. This measures the fluid-filled space at the back of the baby’s neck. A measurement above 3 millimeters at 12 weeks can signal a higher chance of chromosomal conditions like Down syndrome. The scan is often combined with a blood test for more accurate screening. It’s not required, but if you opt in, it adds one more ultrasound to your total. In many practices this scan is done at the same appointment as the dating scan, so you may not even realize they’re separate assessments.
Why Some Pregnancies Need More Scans
A pregnancy classified as high-risk typically means more ultrasounds, sometimes many more. Conditions that trigger extra monitoring include high blood pressure, diabetes, obesity, epilepsy, a history of preterm delivery or preeclampsia, and pregnancies conceived through assisted reproductive technology. Problems that develop during pregnancy, like an unusually positioned placenta, restricted fetal growth (when the baby measures below the 10th percentile for gestational age), or abnormal amniotic fluid levels, also call for additional imaging.
In the third trimester, low-risk pregnancies don’t routinely get another scan unless your provider notices a mismatch between your belly measurement and how far along you are. That discrepancy can suggest the baby is growing too slowly or too quickly, and a growth scan helps clarify what’s happening.
Twin and Multiple Pregnancies
Carrying more than one baby raises the risk of complications, and the ultrasound schedule reflects that. How often you’re scanned depends largely on whether the babies share a placenta.
- Separate placentas (dichorionic-diamniotic): Ultrasounds typically start at 24 weeks and repeat every 4 weeks for uncomplicated pregnancies.
- Shared placenta (monochorionic-diamniotic): Monitoring starts earlier, at 16 weeks, with scans every 2 weeks to check each baby’s bladder and amniotic fluid levels. Growth is assessed every 4 weeks or more often if anything looks abnormal.
- Shared placenta and shared sac (monochorionic-monoamniotic): These pregnancies carry the highest risk and are scanned even more frequently.
This is in addition to the standard first-trimester and anatomy scans, so twin pregnancies can easily involve six or more ultrasounds total.
Late-Pregnancy Monitoring Scans
If your provider has concerns about how the baby is doing in the third trimester, they may order a biophysical profile. This specialized ultrasound evaluates five things: fetal heart rate, breathing movements, body movements, muscle tone, and the amount of amniotic fluid. Each category gets a score of 0 or 2, for a maximum of 10 points. A high score is reassuring; a low one may prompt further testing or earlier delivery. Some high-risk pregnancies have biophysical profiles weekly or even twice a week in the final stretch.
Are Ultrasounds Safe?
Diagnostic ultrasound has no known harmful effects when performed by trained providers for a medical reason. It uses sound waves rather than radiation, which is why it’s the go-to imaging tool in pregnancy. That said, ultrasound energy can slightly heat tissues and, in some cases, create tiny gas pockets in body fluids. The long-term consequences of these effects aren’t fully understood, which is why medical guidelines follow a principle of keeping exposure as low as reasonably needed: use the lowest power setting that still produces a clear image, and don’t scan longer than necessary.
This is also why the FDA discourages commercial “keepsake” ultrasound sessions at boutique studios. Getting a photo or short video during a medically indicated scan is perfectly fine, but scheduling extra sessions purely for entertainment means additional exposure with no diagnostic benefit. Over-the-counter fetal heartbeat monitors carry similar concerns. They can expose the baby to prolonged energy from untrained use and may produce readings that parents misinterpret.
A Realistic Count by Trimester
For a straightforward, low-risk pregnancy, expect two to three ultrasounds total: the dating scan around 10 to 14 weeks, possibly a nuchal translucency screening around the same time, and the anatomy scan at 18 to 22 weeks. Some providers add a brief scan at the very first visit to confirm a heartbeat, which could push the count to three or four. A high-risk pregnancy can easily double or triple that number depending on the condition being monitored. Your specific count will depend on your health history, how the pregnancy progresses, and your provider’s clinical judgment.