Obstetric Ultrasound
Ultrasound for pregnancy dating, anatomy, and growth.
What is Obstetric?
Obstetric ultrasound uses high-frequency sound waves to create real-time images of the developing fetus, placenta, and maternal structures throughout pregnancy.
How it works: A transducer placed on the abdomen or in the vagina emits sound waves that bounce off fetal structures and return as echoes, which are converted into detailed images allowing visualization of fetal anatomy, growth, and movement.
Common Uses of Obstetric
First-trimester dating and viability
Confirm intrauterine pregnancy, measure crown-rump length for dating, detect heartbeat, and assess yolk sac
Anomaly screening (18-22 weeks)
Detailed anatomy survey including brain, heart, spine, face, and extremities; screen for major structural abnormalities
Growth assessment and Doppler studies
Monitor fetal biometry (head circumference, abdominal circumference, femur length), assess amniotic fluid, evaluate placental location and umbilical artery blood flow
Multiple pregnancy evaluation
Determine chorionicity, amnionicity, fetal positions, and monitor for complications like twin-twin transfusion syndrome
Comprehensive fetal well-being
Biophysical profile, non-stress test, middle cerebral artery Doppler for growth restriction, and ductus venosus assessment
Advantages
- ✓No ionizing radiation - completely safe for mother and fetus
- ✓Real-time imaging allows assessment of fetal activity and well-being
- ✓Excellent visualization of fetal anatomy with modern equipment
- ✓Can be performed transabdominally or transvaginally as needed
- ✓Provides both structural and functional information
- ✓Lower cost compared to prenatal MRI
Limitations
- ⚠Limited by maternal body habitus and fetal position
- ⚠Early pregnancy viability may require transvaginal approach
- ⚠Certain maternal conditions (fibroids, obesity) can limit visualization
- ⚠Cannot detect all structural abnormalities
- ⚠Operator skill affects image quality and diagnostic accuracy
Preparation Checklist
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⚖️Obstetric vs MRI
| Criteria | Obstetric | MRI |
|---|---|---|
| Speed | Moderate | Moderate |
| Radiation | No | Yes |
| Soft Tissue Detail | Limited | Excellent |
| Cost | Low | High |
Related Imaging Modalities
Prenatal MRI provides complementary detail for brain abnormalities. CT is rarely used in pregnancy due to radiation.
MRI
MRI uses powerful magnets and radio waves to produce detailed images of organs and soft tissues. Excellent for brain, spine, and joint imaging.
CT
CT scans use X-rays to create detailed cross-sectional images of the body. They are particularly useful for detecting bone fractures, tumors, and internal bleeding.
Browse Obstetric Terms
Explore common terms in Obstetric reports, each with detailed explanations, clinical significance, and related lab tests to help you understand your imaging results. lab tests.
Fetal Anomaly Scan: What It Shows, Cost & Preparation
Systematic evaluation of fetal anatomy, biometry, and placental position
Fetal Growth Restriction Scan: What It Shows, Cost & Prepara
Disproportionately small fetal measurements, abnormal Doppler waveforms
First Trimester Dating Ultrasound: What It Shows, Cost & Pre
Gestational sac, yolk sac, fetal pole with cardiac activity; crown-rump length measurement for dating
Nuchal Translucency Ultrasound: What It Shows, Cost & Prepar
Measurement of fluid collection at posterior aspect of fetal neck; increased nuchal translucency associated with aneuploidy risk
Third Trimester Growth Ultrasound: What It Shows, Cost & Pre
Fetal size assessment via biometry, amniotic fluid volume, placental grading, and Doppler evaluation of fetal and placental circulation
Placenta Previa Scan: What It Shows, Cost & Preparation
Placental tissue covering or adjacent to internal cervical os
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