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Exam Review

Key Facts: RDMS OB/GYN Exam

170

Exam Questions

ARDMS

555

Passing Score (scaled)

ARDMS (300-700 scale)

3 hrs

Exam Duration

ARDMS

$300

Specialty Exam Fee

ARDMS

37%

2nd/3rd Trimester OB

Largest domain

3-year

CME Cycle

Inteleos (plus annual renewal)

The RDMS OB/GYN exam has approximately 170 questions in 3 hours, scored on a 300-700 scale with 555 needed to pass (not a percentage). Five domains: Second/Third Trimester OB (37%), Protocols & Procedures (24%), Gynecology (19%), First Trimester OB (12%), and Physics & Instrumentation (8%). RDMS requires the SPI exam and the specialty exam within five years of each other, in either order. $300 specialty exam fee. Certification is maintained with annual renewal and CME in three-year cycles.

Sample RDMS OB/GYN Practice Questions

Try these sample questions to review concepts for the RDMS OB/GYN exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 200+ question experience with AI tutoring.

1What is the normal sonographic appearance of the endometrium during the menstrual phase?
A.Thick and hyperechoic
B.Thin and hyperechoic line
C.Thick and hypoechoic
D.Trilaminar appearance
Explanation: During the menstrual phase (days 1-5), the endometrium appears as a thin, echogenic line measuring 1-4 mm due to sloughing of the functionalis layer. The thick hyperechoic appearance describes the secretory phase, while the trilaminar appearance is characteristic of the late proliferative phase around ovulation.
2Which ligament extends from the lateral aspect of the uterus to the pelvic sidewall and contains the uterine artery?
A.Round ligament
B.Broad ligament
C.Cardinal ligament
D.Uterosacral ligament
Explanation: The cardinal (Mackenrodt) ligament extends from the lateral cervix and upper vagina to the pelvic sidewall and contains the uterine artery and veins. The broad ligament is a peritoneal fold, the round ligament extends anteriorly to the labia majora, and the uterosacral ligaments extend posteriorly to the sacrum.
3In a premenopausal patient, what is the normal maximum anteroposterior diameter of the endometrium during the secretory phase?
A.4-6 mm
B.7-10 mm
C.12-16 mm
D.20-25 mm
Explanation: During the secretory phase, the endometrium normally measures 12-16 mm in maximum thickness due to progesterone-induced glandular secretion and edema. A measurement greater than 16 mm is generally considered thickened in premenopausal women and warrants further evaluation.
4Which ovarian structure is identified sonographically as a small cystic structure typically measuring 2-3 cm that may contain a hyperechoic mural nodule (cumulus oophorus) at ovulation?
A.Corpus luteum cyst
B.Follicular cyst
C.Theca lutein cyst
D.Paraovarian cyst
Explanation: The corpus luteum cyst forms after ovulation and typically measures 2-3 cm with thick, crenulated walls. The cumulus oophorus may be visible as a small hyperechoic mural nodule. These cysts demonstrate prominent peripheral vascularity on Doppler (ring of fire). Follicular cysts are simple and thin-walled, while theca lutein cysts are associated with high hCG levels.
5What is the normal position of the ovaries relative to the uterus in the adult female pelvis?
A.Anterior to the uterus
B.Posterior and lateral to the uterus
C.Superior to the uterine fundus
D.Within the uterine cornua
Explanation: The ovaries are typically located posterior and lateral to the uterus, within the ovarian fossa on the lateral pelvic sidewall. Their position can vary with uterine position and patient positioning. The ovaries are suspended by the mesovarium portion of the broad ligament.
6During which phase of the menstrual cycle does the endometrium demonstrate the classic "trilaminar" or "three-line" sign?
A.Early proliferative phase
B.Late proliferative phase
C.Early secretory phase
D.Menstrual phase
Explanation: The trilaminar sign appears during the late proliferative phase (periovulatory period) when estrogen stimulation causes the functionalis layers to become hypoechoic, flanking the echogenic central interface. This finding indicates a receptive endometrium and typically occurs around days 14-16 of a 28-day cycle.
7What is the normal postmenopausal endometrial thickness threshold above which further evaluation is typically recommended?
A.3 mm
B.5 mm
C.8 mm
D.12 mm
Explanation: In postmenopausal women with bleeding, an endometrial thickness greater than 5 mm generally requires further evaluation (such as sonohysterography or endometrial biopsy) to exclude endometrial hyperplasia or carcinoma. In asymptomatic postmenopausal women, thresholds up to 8 mm may be acceptable depending on clinical context.
8The uterine artery typically branches from which major vessel?
A.Ovarian artery
B.Internal iliac (hypogastric) artery
C.External iliac artery
D.Inferior mesenteric artery
Explanation: The uterine artery arises from the anterior division of the internal iliac (hypogastric) artery. It crosses superior to the ureter approximately 2 cm lateral to the cervix ("water under the bridge"), then ascends along the lateral uterine margin to anastomose with the ovarian artery at the uterine cornu.
9What is the most common benign gynecologic tumor in women of reproductive age?
A.Ovarian cyst
B.Endometrial polyp
C.Uterine leiomyoma (fibroid)
D.Cervical polyp
Explanation: Uterine leiomyomas (fibroids) are the most common benign gynecologic tumors, affecting 20-30% of women of reproductive age. They arise from smooth muscle cells of the myometrium and are hormonally responsive, typically enlarging during pregnancy and regressing after menopause.
10Which sonographic finding is characteristic of a submucosal leiomyoma?
A.Uterine enlargement with heterogeneous myometrium
B.Well-defined hypoechoic mass distorting the endometrial cavity
C.Cystic adnexal mass separate from the ovary
D.Diffuse uterine enlargement with indistinct endometrium
Explanation: Submucosal leiomyomas are located just beneath the endometrium and project into the uterine cavity. Sonographically, they appear as well-defined, typically hypoechoic masses that distort the endometrial cavity. They are the most likely type to cause abnormal uterine bleeding due to their location.

About the RDMS OB/GYN Exam

The RDMS OB/GYN exam validates expertise in obstetric and gynecologic sonography including first trimester evaluation, second/third trimester fetal assessment, gynecologic pelvic anatomy, scanning protocols, and ultrasound physics. It is the most popular ARDMS specialty exam.

Exam sponsor: ARDMS (American Registry for Diagnostic Medical Sonography) / Pearson VUE. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Questions

170 questions

Time Limit

3 hours

Passing Score

Scaled score 555 (300-700 scale)

Exam / Certification Fees

$300

Exam sponsor website

Reported exam pass rate: 79%. 2023 first-time takers (Inteleos) This describes exam candidates, not OpenExamPrep users or results from using our resources. Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

37%

Second/Third Trimester Obstetrics

Fetal biometry, fetal anatomy, fetal anomalies, multiple gestations, placenta, amniotic fluid, biophysical profile

19%

Gynecology - Pelvic Anatomy

Normal pelvic anatomy, uterine pathology, ovarian pathology, adnexal masses, postmenopausal findings

24%

Protocols and Procedures

Scanning techniques, patient care, measurement standards, documentation, first trimester screening, safety

12%

First Trimester Obstetrics

Early pregnancy, embryology, CRL measurement, NT screening, viability assessment, ectopic pregnancy

8%

Physics and Instrumentation

Doppler principles, hemodynamics, image optimization, artifacts, transducer physics, bioeffects

Preparing for the RDMS OB/GYN Exam

What You Need to Know

  • Passing score: Scaled score 555 (300-700 scale)
  • Exam length: 170 questions
  • Time limit: 3 hours
  • Exam / certification fees: $300 Official sources

Using Our Practice Resources

  • Work through all 200 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

RDMS OB/GYN: Suggested Study Strategy

1Focus on Second/Third Trimester OB (37%) — master fetal biometry (BPD, HC, AC, FL), anatomy survey, and anomaly recognition
2Study Protocols & Procedures (24%) — measurement standards, patient care, documentation, and safety considerations
3Know gynecologic pathology: fibroids, adenomyosis, ovarian cysts, PCOS, endometrial pathology, and adnexal masses
4Master first trimester concepts: CRL measurement, NT screening criteria, viability assessment, and ectopic pregnancy recognition
5Understand Doppler principles: umbilical artery, uterine artery, and MCA waveforms and their clinical significance
6Review ALARA principles and bioeffects — thermal and mechanical indices for safe ultrasound practice

Frequently Asked Questions

What is the RDMS OB/GYN exam?

RDMS OB/GYN is an ARDMS specialty exam that validates expertise in obstetric and gynecologic sonography. It covers fetal assessment, pelvic anatomy evaluation, scanning protocols, and ultrasound physics. It is the most popular RDMS specialty.

How many questions are on the RDMS OB/GYN exam?

The exam has approximately 170 multiple-choice and hotspot questions in 3 hours. Scores are reported on a 300-700 scale and 555 or better passes; the score is not a percentage. It is taken at Pearson VUE test centers.

What are the prerequisites for the RDMS OB/GYN exam?

RDMS certification requires the SPI (Sonography Principles & Instrumentation) exam and a specialty exam such as OB/GYN, passed within five years of each other in either order. Applicants must also meet an ARDMS prerequisite pathway of education and clinical experience. The OB/GYN exam fee is $300.

What is the hardest part of the RDMS OB/GYN exam?

Second/Third Trimester Obstetrics (37%) is both the largest and most challenging domain. It requires mastery of fetal biometry (BPD, HC, AC, FL), fetal anomaly recognition, placental abnormalities, and amniotic fluid assessment.

How should I prepare for the RDMS OB/GYN exam?

Plan for 150-250 hours of study over 8-12 weeks. Focus on Second/Third Trimester OB (37%) and Protocols & Procedures (24%) — together 61% of the exam. Master fetal biometry measurements, anomaly detection, and scanning technique standards.