RadteraUltrasound Obstetric Second/Third Trimester (Standard)
USNo contrastOB-GYN
Indications
- Routine anatomic survey (typically 18-22 weeks)
- Fetal growth assessment
- Amniotic fluid evaluation
- Placental location
- Confirm dates / fetal number / presentation
- Follow-up of known abnormality
Patient prep
- Generally none; moderately full bladder may help cervix/lower uterine segment early in second trimester
Contrast
None / non-contrast
Technique
- Curvilinear 2-5 MHz transducer; transvaginal for cervical length/placenta previa as needed
- Maternal supine/left lateral tilt for comfort
- ALARA; spectral/color Doppler only when clinically indicated (e.g., growth restriction)
Series / Sequences
| # | Series / Sequence | Plane | Notes |
|---|---|---|---|
| 1 | Fetal number, presentation, cardiac activity | As needed | Document; rate |
| 2 | Biparietal diameter (BPD) | Transthalamic axial | Biometry |
| 3 | Head circumference (HC) | Transthalamic axial | Biometry |
| 4 | Abdominal circumference (AC) | Axial at stomach/portal vein | Biometry |
| 5 | Femur length (FL) | Long axis of femur | Biometry; estimated fetal weight calculated from BPD/HC/AC/FL |
| 6 | Cerebral - lateral ventricles, choroid plexus, cavum septi pellucidi | Axial | Atrium normal <10 mm |
| 7 | Posterior fossa - cerebellum, cisterna magna | Axial | Anatomy |
| 8 | Face - upper lip / nose | Coronal | Cleft screening |
| 9 | Neck / nuchal fold | Axial | If indicated |
| 10 | Four-chamber heart and outflow tracts (LVOT/RVOT) | Axial | Cardiac screening; 3-vessel view |
| 11 | Chest / lungs and diaphragm | Axial/sagittal | Anatomy |
| 12 | Abdomen - stomach, kidneys, bladder, cord insertion | Axial | Anatomy; vessel number in cord |
| 13 | Spine - cervical to sacral | Sagittal and transverse | Anatomy |
| 14 | Extremities | As needed | Presence of arms/legs |
| 15 | Placenta - location and relationship to internal os | Sagittal | Document; cord insertion |
| 16 | Amniotic fluid | As needed | Single deepest pocket or AFI |
| 17 | Cervix (when indicated) | Sagittal (TV if needed) | Length |
| 18 | Fetal sex (if requested/medically indicated) | Axial | Optional |
Key points
- Standard biometry: BPD, HC, AC, FL — used for growth and estimated fetal weight
- Document anatomic survey of head, face, neck, chest/heart, abdomen, spine, extremities, and genitalia as feasible
- Assess placental location relative to internal os; report low-lying placenta/previa
- Add umbilical artery / MCA Doppler for suspected growth restriction
References
• AIUM Practice Parameter for the Performance of Standard Diagnostic Obstetric Ultrasound Examinations, 2024 (ACR-ACOG-AIUM-SRU) link
• AIUM Practice Parameter for the Performance of Detailed Second- and Third-Trimester Diagnostic Obstetric Ultrasound (2019)
• Radiopaedia: Second trimester ultrasound link
• AIUM Practice Parameter for the Performance of Detailed Second- and Third-Trimester Diagnostic Obstetric Ultrasound (2019)
• Radiopaedia: Second trimester ultrasound link
Source: Researched — verify against your institution
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Reference template — verify and adapt to your scanner, vendor and institution before clinical use. Not a substitute for clinical judgment.