The anatomy scan, typically performed around 18 to 22 weeks of pregnancy, is one of the most anticipated—and sometimes nerve-wracking—prenatal appointments. For many parents, it’s the first detailed look at their baby as a recognizable person, and it may also be when they learn the sex if they wish. For women over 35, the anatomy scan carries the same fundamental purpose as it does for any pregnant person, with potentially some additional context around what the imaging can and cannot reveal.
Understanding what the anatomy scan actually evaluates, how results are interpreted, and what happens when something requires further review can help reduce some of the anxiety surrounding this appointment. While no single ultrasound can guarantee a perfect outcome, the anatomy scan provides valuable information and is a standard component of prenatal care.
What the Anatomy Scan Actually Evaluates
The anatomy scan is a detailed ultrasound examination conducted by a sonographer and reviewed by your OB/GYN, maternal-fetal medicine (MFM) specialist, or radiologist. Despite sometimes being called the “20-week ultrasound,” it’s not just a photo opportunity—it’s a systematic evaluation of fetal anatomy. According to the American College of Obstetricians and Gynecologists, the standard anatomy scan includes assessment of the following areas:
The scan evaluates the fetal brain structures (including the cerebral ventricles, corpus callosum, cerebellum, and spine), facial features, heart (including the four chambers and major blood vessels), abdominal organs (stomach, kidneys, bladder), limbs and extremities, and placenta position and amniotic fluid levels. The sonographer will also measure the baby’s growth (head circumference, abdominal circumference, femur length) to confirm development is progressing appropriately.
How Long Does It Take?
A complete anatomy scan typically takes 20 to 45 minutes, though this varies depending on the baby’s position, maternal body habitus, and how cooperative the baby is being during the exam. Sometimes the technician needs to have you move positions or come back another time if the baby isn’t positioned in a way that allows all structures to be visualized clearly—this is common and doesn’t indicate a concern.
Soft Markers and What They Mean
One area that causes significant anxiety for many pregnant women, particularly those who’ve had first-trimester screening, is the potential finding of “soft markers.” These are ultrasound findings that, in isolation, are often normal variants or incidental findings in otherwise healthy fetuses—but that have historically been associated with a slightly elevated statistical likelihood of chromosomal differences.
Common soft markers include a bright spot in the heart (echogenic intracardiac focus or EIF), bright areas in the bowel (echogenic bowel), mild kidney pelvis dilation (pyelectasis), short femur or humerus, and choroid plexus cysts. The interpretation of soft markers has evolved considerably over the past decade. For women with low-risk cfDNA (cell-free DNA) screening results or other low-risk first-trimester screening, many soft markers in isolation carry very limited predictive value and are unlikely to change clinical management.
Your healthcare provider is best positioned to contextualize any findings from your anatomy scan in light of your complete screening history, age, and overall clinical picture. This is a nuanced area where discussion with your provider—and sometimes a maternal-fetal medicine specialist—adds much more clarity than any general information can provide.
When Further Evaluation Is Recommended
If the anatomy scan reveals findings that need further evaluation, your provider may recommend additional imaging (a targeted ultrasound or fetal echocardiogram, for example), consultation with a maternal-fetal medicine (MFM) specialist, or additional testing. This doesn’t necessarily mean something is definitively wrong—anatomy scans are screening tools, and findings sometimes require more detailed assessment to characterize accurately.
Women who haven’t had first-trimester genetic screening or cfDNA testing may be offered diagnostic genetic testing at this stage if anatomy findings raise concerns. For women over 35 who are considering genetic testing options, discussing the timing and type of testing with your provider early in prenatal care ensures you’re making informed decisions at each stage.
Placenta Position and Amniotic Fluid
The anatomy scan also evaluates where the placenta is located and whether amniotic fluid levels are within a normal range. If the placenta appears to be covering or close to the cervix (a finding called placenta previa), a follow-up ultrasound later in pregnancy is standard, as many low-lying placentas resolve as the uterus grows. Most cases of apparent placenta previa at 20 weeks do not persist to the third trimester.
Amniotic fluid assessment provides another data point about fetal well-being and is one of many factors your provider monitors across prenatal visits and third-trimester monitoring. Both too little (oligohydramnios) and too much (polyhydramnios) amniotic fluid may warrant additional evaluation if present.
The Emotional Experience of the Anatomy Scan
It’s worth acknowledging that the anatomy scan is emotionally charged for many women, particularly those who have experienced pregnancy loss, fertility challenges, or significant anxiety during pregnancy. The combination of anticipation about seeing the baby and awareness that the scan is looking for problems can create a complicated emotional experience.
Some women find it helpful to go into the appointment informed about what the scan evaluates but not hyper-focused on every possible finding. Others appreciate having a support person present. If you find that pregnancy anxiety is significantly affecting your wellbeing, discussing this with your provider or a mental health professional who works with perinatal concerns can be valuable—anxiety during pregnancy is common and treatable.
Frequently Asked Questions
Can the anatomy scan detect all birth defects?
No—the anatomy scan evaluates the structures that are visible on ultrasound at 18 to 22 weeks, but it cannot detect all conditions or genetic differences. Some findings may not be visible at this stage, and certain conditions affect physiology rather than visible anatomy. It’s an important screening tool, not a guarantee of a perfect outcome, and should be understood in that context.
Do I need to have a full bladder for the anatomy scan?
Unlike early pregnancy ultrasounds done abdominally, the anatomy scan at 18 to 22 weeks typically doesn’t require a full bladder—by this stage, the uterus is large enough to be imaged clearly. Check with your provider’s office beforehand, as practices may vary. Wearing comfortable clothing with an accessible belly makes the exam easier.
What if the baby doesn’t cooperate during the scan?
It’s very common for babies to be in positions that make certain structures difficult to visualize—they move, sleep, or face away from the ultrasound probe. The sonographer will try different approaches and positions to get needed views. Sometimes a follow-up scan is scheduled if certain structures can’t be adequately visualized—this is routine and not a cause for concern in itself.
Can I find out the sex at the anatomy scan?
Yes, the anatomy scan can typically identify fetal sex if the baby is in a position where the genitals are visible and if you wish to know. If you’d prefer not to know, simply let your sonographer and provider know beforehand. Some parents choose to have the sex revealed to them in a specific way, and this can often be accommodated.
Key Takeaways
- The anatomy scan at 18 to 22 weeks is a detailed evaluation of fetal structures, not just a gender reveal—it provides important information about development and organ formation.
- “Soft markers” require context to interpret meaningfully; for women with low-risk first-trimester screening, isolated soft markers often have limited clinical significance.
- Findings requiring further evaluation don’t necessarily indicate a serious problem—follow-up imaging or specialist consultation provides more information to characterize findings accurately.
- Placenta position findings (like low-lying placenta) at 20 weeks often resolve by the third trimester and are monitored with follow-up imaging.
- Discussing any findings or concerns directly with your provider—ideally with a maternal-fetal medicine specialist if indicated—provides the most accurate and personalized guidance for your situation.
Medical Disclaimer
This content is for informational purposes only and does not constitute medical advice. Individual health situations vary significantly. Always consult a qualified healthcare provider before making decisions related to your health, fertility, or pregnancy.
About the Author
Emily Carter is a women’s health writer focused on fertility, pregnancy after 35, and sleep changes in midlife. She writes research-informed, non-alarmist content to help women navigate reproductive and hormonal transitions with clarity and confidence.