Most pregnant people get two routine ultrasounds: a dating scan in the first trimester and an anatomy scan between 18 and 22 weeks. Beyond those two, your next ultrasound depends on how your pregnancy is progressing, whether any complications arise, and what your provider saw on earlier scans. If you’re not pregnant and are tracking something like an ovarian cyst or gallbladder polyp, follow-up timing depends on what was found and its size.
The Two Standard Pregnancy Ultrasounds
The first routine ultrasound typically happens in the first trimester, up through about 13 weeks. This is the most accurate time to confirm your due date, because early measurements of the embryo are precise to within about five to seven days. If your provider offers screening for chromosomal conditions, this scan may be combined with a nuchal translucency measurement between weeks 11 and 13, which checks the fluid at the back of the baby’s neck.
The second routine scan is the anatomy scan, sometimes called the anomaly scan or the “20-week ultrasound.” It’s typically scheduled between 18 and 22 weeks. This is the longer, more detailed appointment where a sonographer checks the baby’s brain, heart, spine, kidneys, limbs, and other structures. It also evaluates the placenta’s position and your amniotic fluid levels. About 12% of anatomy scans come back incomplete, usually because the baby was in a position that blocked the view of a particular organ. If that happens, you’ll be asked to come back for a follow-up, often one to two weeks later. Higher BMI, earlier gestational age at the time of the scan, and simple bad luck with fetal positioning are the most common reasons for a redo.
Third Trimester Scans
In a straightforward, low-risk pregnancy, many providers don’t schedule another ultrasound after the anatomy scan. But there are several reasons one might be added in the third trimester.
When a third-trimester scan is ordered, it has traditionally been done around 32 to 34 weeks. At that stage, there’s still enough amniotic fluid to get a clear picture and the baby hasn’t yet curled into a tightly flexed position. For low-risk pregnancies where the goal is simply to check growth, scanning closer to 36 weeks may actually be more accurate at catching babies who are measuring too small or too large. For higher-risk pregnancies, 32 weeks or even earlier is more common.
Common reasons for a third-trimester ultrasound include vaginal bleeding, a placenta that was sitting low at the anatomy scan, reduced fetal movement, concern that the baby is growing too quickly or too slowly based on your belly measurements, or a history of complications in a prior pregnancy.
High-Risk Pregnancies Mean More Frequent Scans
If you have a condition that can affect how the baby grows or how much amniotic fluid surrounds it, such as diabetes, high blood pressure, or a multiple pregnancy, expect ultrasounds throughout the third trimester. Some practices schedule these every two weeks, others every three to four weeks. The goal is to monitor whether the baby’s growth is on track and whether fluid levels remain normal.
If your baby has been diagnosed with fetal growth restriction, meaning they’re measuring significantly small for their gestational age, the monitoring schedule tightens further. Doppler ultrasound of the umbilical artery, which measures how well blood is flowing through the cord, is recommended every one to two weeks once growth restriction is confirmed. This helps your provider catch any deterioration early enough to act.
Past Your Due Date
Once you reach 41 weeks or beyond, your provider will likely recommend a biophysical profile. This combines a short ultrasound with a non-stress test to check on the baby’s movement, muscle tone, breathing-like motions, and amniotic fluid. It can be scheduled once or twice a week until delivery. The ultrasound portion is quick, usually just a few minutes, and is mainly looking for signs that the baby is still doing well in an aging placental environment.
If You’re Monitoring an Ovarian Cyst
If you’re not pregnant and had an ultrasound that found an ovarian cyst, the follow-up schedule depends on the cyst’s size and whether you’re pre- or postmenopausal.
- Premenopausal, cyst 5 cm or smaller: No follow-up needed. Cysts up to 3 cm are considered normal physiologic findings, and those between 3 and 5 cm are almost certainly benign.
- Premenopausal, cyst between 5 and 7 cm: A yearly follow-up ultrasound is recommended.
- Premenopausal, cyst larger than 7 cm: Further imaging with MRI or a surgical evaluation may be suggested, since ultrasound alone may not fully characterize larger cysts.
- Postmenopausal, cyst 1 cm or smaller: No follow-up needed.
- Postmenopausal, cyst between 1 and 7 cm: Yearly ultrasound follow-up is recommended, at least initially. Once the cyst has been stable or shrinking on repeat scans, the interval may be extended.
Gallbladder Polyp Monitoring
If a gallbladder polyp was found incidentally on a prior ultrasound, the surveillance schedule depends on polyp size and your risk factors for gallbladder cancer (which include being over 50, having gallstones, or having a polyp that’s growing). For polyps between 6 and 9 mm with no risk factors, or polyps 5 mm and under with risk factors, follow-up ultrasounds are recommended at 6 months, 1 year, and 2 years. If a polyp grows by 2 mm or more during that two-year window, your provider will reassess based on its current size and your overall risk profile.
Why Your Schedule Might Differ From Someone Else’s
Ultrasound schedules vary more than most people expect. Two people at the same stage of pregnancy, seeing providers in the same city, can have very different scan timelines. Some of this comes down to clinical judgment: one provider may want another look at a borderline finding while another is comfortable waiting. Insurance coverage, practice style, and available equipment also play a role. If you’re unsure why a scan was or wasn’t scheduled, asking your provider directly is the fastest way to get a clear answer specific to your situation.