Most pregnant women get at least two routine ultrasounds: the first between 10 and 13 weeks, and the second between 18 and 22 weeks. Beyond those two, your exact schedule depends on whether your pregnancy is considered low-risk or high-risk, and your provider’s own practice style. Some clinics add a third scan around 36 weeks, while high-risk pregnancies may involve scans every few weeks in the final trimester.
First Trimester: The Dating Scan (10 to 13 Weeks)
Your first ultrasound typically happens between 10 and 13 weeks. Its main job is to confirm how far along you are by measuring the baby from head to rump. This measurement, taken in the first trimester, is the most accurate way to establish a due date, with a margin of error of only five to seven days. The earlier in the first trimester the scan is done, the more precise that estimate becomes.
This scan also confirms the number of babies, checks for a heartbeat, and rules out an ectopic pregnancy. If you’re at least 11 weeks along, the technician can also measure a small pocket of fluid at the back of the baby’s neck. This screening helps estimate the chance of certain chromosomal conditions like Down syndrome. The measurement must be taken before 13 weeks and 6 days to be reliable, so timing matters.
Because the baby is still small at this stage, some providers use a transvaginal probe rather than the standard wand on your belly. Transvaginal imaging produces a clearer picture in pregnancies under 10 weeks, in patients with a higher body weight, and when the uterus tilts backward. It’s painless, though it can feel a bit awkward. By around 12 to 13 weeks, most providers switch to abdominal imaging for the rest of the pregnancy.
Second Trimester: The Anatomy Scan (18 to 22 Weeks)
The anatomy scan is the one ultrasound that virtually every pregnancy includes. ACOG, the leading professional group for obstetricians in the U.S., recommends that all pregnant women have at least one standard ultrasound at 18 to 22 weeks. This is the most detailed scan of the entire pregnancy, and it often takes 30 to 45 minutes.
The sonographer will methodically examine the baby’s bones, heart, brain, spinal cord, face, kidneys, and abdomen. They also check the placenta’s position and the blood flow in your uterus. Don’t be alarmed if the technician goes quiet for stretches of time. They’re concentrating on specific structures and taking precise measurements. If the baby cooperates, this is also the scan where you can find out the sex.
Occasionally the sonographer can’t get a clear view of every structure, usually because of the baby’s position. If that happens, you may be asked to come back a week or two later for a follow-up look at whatever was missed.
Third Trimester: Growth and Position Checks (28 to 37 Weeks)
Third-trimester scans are not universal for low-risk pregnancies, but many providers include at least one. Around 36 weeks, your provider may do a quick ultrasound to confirm the baby is head-down and in position for delivery. This scan is also useful for estimating the baby’s weight, checking the amount of amniotic fluid, and assessing placental health.
Research involving more than 100,000 women found that standard ultrasound at 35 to 37 weeks reveals a significant number of structural issues for the first time, ones that weren’t visible earlier. Weight estimates taken at this stage also correlate more closely with actual birth weight than those taken at 30 to 33 weeks. International guidelines now recommend that screening for babies who are unusually small or large be done at 36 weeks rather than 32, because accuracy improves substantially later in the trimester. Detection rates for small-for-gestational-age babies nearly doubled when scanning moved from 32 weeks to 36 weeks in one randomized trial.
If you had a low-lying placenta noted at your anatomy scan, expect a repeat check around 32 weeks and potentially another at 36 weeks to help plan your delivery.
When You’ll Get More Frequent Scans
Certain conditions trigger additional monitoring throughout pregnancy. You’re likely to have more ultrasounds if you’re carrying twins or multiples, have gestational diabetes, have high blood pressure or preeclampsia, are over 35, have a history of pregnancy complications, or if your baby’s growth seems off-track at any point.
In these situations, your provider may order growth scans every two to four weeks in the third trimester. Some of these appointments include a biophysical profile, a specialized scan that scores five aspects of your baby’s well-being: heart rate, breathing movements, body movements, muscle tone, and the volume of amniotic fluid. Each category gets a score of 0 or 2, for a possible total of 10. A score of 8 or 10 is reassuring. Lower scores may prompt further testing or closer monitoring.
A Typical Low-Risk Schedule at a Glance
- 10 to 13 weeks: Dating scan to confirm due date, check heartbeat, and screen for chromosomal markers
- 18 to 22 weeks: Anatomy scan to examine organs, bones, placenta, and (optionally) determine sex
- 36 weeks (if offered): Position check, growth estimate, and amniotic fluid assessment
Some providers order an early scan before 10 weeks if you have bleeding, pain, uncertain dates, or a history of miscarriage. Others skip the third-trimester scan entirely for straightforward pregnancies. Your actual number of ultrasounds could range from one to a dozen or more depending on how your pregnancy unfolds. Each scan is scheduled with a specific clinical question in mind, so if your provider orders an extra one, it doesn’t automatically mean something is wrong. It often just means they want a clearer picture.