Prenatal Ultrasounds — What Each One Is For — Evidence Library

What it is

Standard prenatal care in most places includes 1–2 medical ultrasounds: a DATING scan in the first trimester (most accurate dating), and an ANATOMY scan at 18–22 weeks (checks fetal structures head-to-toe). Depending on your history and screening choices, you may also have an NT scan (11–13 weeks, part of first-trimester screening), growth scans (later, if size or risk suggests it), or biophysical profiles (BPP — movement, tone, breathing, fluid, sometimes NST) in high-risk situations. Non-medical 3D/4D 'keepsake' scans are common but not recommended by the FDA or ACOG as routine — the safety data is based on medical, time-limited scans.

Evidence review links

Each link opens the full review on the publisher's site in a new tab.

Possible benefits

Dating scan: most accurate way to set the due date and detect twins earlyReview sources ↓
Anatomy scan: catches most major structural anomalies (heart, spine, brain, kidneys) when it mattersReview sources ↓
Growth scans and BPP: reassure or trigger action in high-risk pregnanciesReview sources ↓
For many families, seeing the baby is a meaningful moment — bring your partner or a support personReview sources ↓

Possible risks

Ultrasound uses sound, not radiation, and has decades of safety data — but 'ALARA' (as low as reasonably achievable) still applies, so more isn't betterReview sources ↓
Anatomy scans detect most, not all, anomalies (~50–80% depending on system and body habitus)Review sources ↓
'Soft markers' (choroid plexus cysts, echogenic bowel, short femur) frequently cause worry without meaning anything — ask about positive predictive value for YOUReview sources ↓
Non-medical keepsake ultrasounds can be reassuring OR cause anxiety; the FDA discourages them because operators are unregulated and use time variesReview sources ↓

Alternatives

Decline any ultrasound (unusual but a real choice)Review sources ↓
The two-scan default (dating + anatomy) for low-risk pregnancyReview sources ↓
NIPT + anatomy scan instead of NT scan (shifts information earlier)Review sources ↓
For 'wanting more pictures': ask if your anatomy scan center offers extra images at the medical scan rather than a separate keepsake studioReview sources ↓

Current evidence

AIUM (American Institute of Ultrasound in Medicine) and ACOG jointly publish the ultrasound practice parameters (dating, first-trimester, standard mid-trimester, targeted). SMFM addresses growth scans and BPP. The FDA has published cautions about non-medical ultrasound. Cochrane reviews support routine dating scans; routine third-trimester scans in LOW-risk pregnancy do not clearly improve outcomes.

Where the evidence is clear · where people may choose differently

For most topics, guidelines from ACOG, WHO, and other major bodies broadly agree on the core safety points (when to act in an emergency, informed-consent standards, monitoring baselines). Where reasonable people — and even guidelines — differ tends to be around thresholds (when to start or stop something), preferences (comfort, environment, support), and values (how you weigh small risks against benefits). Use the questions below to explore those pieces with your care team.

Educational only. Your care team can help you weigh what applies to your specific situation.