OB/GYN vs PS: ARDMS Exam Comparison
This page compares the ARDMS Obstetrics & Gynecology (OB/GYN) and Pediatric Sonography (PS) exams side by side. They differ in clinical scope, content focus, career setting, and 2025 pass-rate data.
OB/GYN vs PS: Exam Comparison
| Factor | Obstetrics & Gynecology (OB/GYN) | Pediatric Sonography (PS) |
|---|---|---|
| Credential earned | RDMS | RDMS |
| Question count | 170 | 170 |
| Exam duration | 3 hours | 3 hours |
| Passing score | 555/700 | 555/700 |
| 2025 first-time pass rate | 80% | 71% |
| 2025 repeat pass rate | 50% | 44% |
| 2025 overall pass rate | 75% | 65% |
| Difficulty level | Easier | Moderate |
Source: ARDMS/APCA Global Exam Performance Summary Report, 2025. First-time and repeat rates describe different candidate groups and do not by themselves establish exam difficulty.
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 Pediatric Sonography (PS) Exam
The ARDMS Pediatric Sonography (PS) specialty exam tests age-specific anatomy, neonatal pathology, and clinical skills that differ fundamentally from adult sonography. Key content areas include neonatal cranial ultrasound, developmental dysplasia of the hip (DDH), pyloric stenosis, and the spectrum of pediatric abdominal and genitourinary pathology.
Key Topics Compared
OB/GYN Key Topics
- First trimester assessment
- Fetal biometry
- Placental evaluation
- Amniotic fluid assessment
- Ectopic pregnancy
- Uterine pathology
- Ovarian pathology
- Cervical assessment
- Multiple gestation
- Fetal anatomy survey
- Growth restriction
- Gynecologic imaging
PS Key Topics
- Neonatal cranial ultrasound
- Intraventricular hemorrhage
- Periventricular leukomalacia
- Pyloric stenosis
- Intussusception
- Hip dysplasia
- Pediatric kidneys
- Appendicitis in children
- Neonatal spine
- Congenital anomalies
- Pediatric liver pathology
- Developmental hip assessment
Among 2025 candidates, OB/GYN first-time and repeat pass rates were 80% and 50% (a 30-point gap); PS rates were 71% and 44% (a 27-point gap). These are separate groups, not a measure of individual improvement.
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 pediatric sonography settings will find the PS exam more immediately supported by their daily practice.
- Career goals: The RDMS (OB/GYN) and RDMS (PS) serve different clinical roles. Consider which aligns better with your desired work environment.
- Pass rate confidence: With a 80% first-time pass rate, OB/GYN may be a confidence-building first exam if you are early in your career. These rates compare separate candidate groups, not the inherent difficulty of an exam.
- Clinical experience: Take the exam that aligns with your strongest clinical rotations or work experience. Hands-on scanning experience impacts exam readiness.
- Prerequisite: Both specialty credentials require a passing SPI score. If you haven't taken the SPI yet, that should be your first priority regardless of specialty choice.
Both exams reward structured, domain-aligned preparation. The PS first-time pass rate is 71% compared with 80% for OB/GYN; use these cohort results as context rather than a prediction of your individual outcome.