OB/GYN vs SPI: ARDMS Exam Comparison
This page compares the ARDMS Obstetrics & Gynecology (OB/GYN) and Sonography Principles & Instrumentation (SPI) exams side by side. Both are ARDMS-administered specialty examinations, but they differ in clinical scope, content focus, career setting, and 2025 pass-rate data.
OB/GYN vs SPI: Exam Comparison
| Factor | Obstetrics & Gynecology (OB/GYN) | Sonography Principles & Instrumentation (SPI) |
|---|---|---|
| Credential earned | RDMS | RDMS/RVT prerequisite |
| Question count | 170 | 110 |
| Exam duration | 3 hours | 2 hours |
| 2025 first-time pass rate | 80% | 74% |
About the Obstetrics & Gynecology (OB/GYN) Exam
The ARDMS OB/GYN specialty exam has the highest first-time pass rate among all seven specialties (80% in 2025), but its content breadth is substantial. It covers the full spectrum of obstetric and gynecologic ultrasound: normal and abnormal pregnancy, fetal anatomy survey, biometry, Doppler surveillance, and gynecologic pathology.
About the Sonography Principles & Instrumentation (SPI) Exam
The ARDMS Sonography Principles and Instrumentation (SPI) exam is the physics prerequisite required before earning any ARDMS specialty credential. It tests sound wave physics, transducer construction, image formation, ultrasound artifacts, Doppler principles, quality assurance, bioeffects, and ALARA safety principles. Unlike specialty exams, the SPI rewards an academic rather than clinical approach.
Which Exam Should You Take First?
The right choice depends on your clinical background, your current employer's needs, and your long-term career goals. Sonographers with strong clinical experience in obstetrics & gynecology imaging should consider the OB/GYN exam first, as applied clinical knowledge transfers directly to board performance. Similarly, those working predominantly in sonography principles & instrumentation settings will find the SPI exam more immediately supported by their daily practice.
Both credentials are valuable additions to a multi-specialty credential portfolio. The 2025 first-time pass rates — 80% for OB/GYN and 74% for SPI — underscore the importance of structured, domain-aligned preparation for whichever exam you choose first.
Dig Deeper Into Each Specialty
- Obstetrics & Gynecology (OB/GYN) exam prep · OB/GYN practice questions
- Sonography Principles & Instrumentation (SPI) exam prep · SPI practice questions
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