How many practice questions should I do for the OB/GYN shelf?

For a standard 4- to 6-week obstetrics and gynecology clerkship, aim for 400 to 600 dedicated practice questions alongside 3 to 4 official NBME Clinical Science Subject Examination forms. Because labor and delivery shifts involve erratic hours and intense emergency cases, micro-batching 15 to 25 questions daily between clinic patients or post-delivery recoveries ensures consistent coverage of high-yield topics like fetal heart tracing interpretation and abnormal uterine bleeding algorithms.

How do I master fetal heart rate tracings for the shelf?

Categorize electronic fetal monitoring tracings according to the official NICHD 3-tier system: Category I (normal, predictive of normal fetal acid-base balance; baseline rate 110–160 bpm, moderate variability, absence of late/variable decels); Category III (abnormal, predictive of abnormal acid-base status; absent variability with recurrent late decels, recurrent variable decels, bradycardia, or sinusoidal pattern; demands immediate intrauterine resuscitation and prompt delivery preparation); and Category II (indeterminate; requires continued surveillance, evaluation, and intrauterine resuscitation). Know your mnemonic VEAL CHOP cold: Variable = Cord compression; Early = Head compression; Acceleration = Okay; Late = Placental insufficiency.

What are the contraindications for common postpartum hemorrhage medications?

The NBME tests the pharmacologic contraindications of second-line uterotonics with extreme frequency: Oxytocin is always first-line for uterine atony; Methylergonovine (Methergine, an ergot alkaloid causing peripheral vasoconstriction) is strictly contraindicated in patients with gestational hypertension, preeclampsia, or coronary disease; Carboprost tromethamine (Hemabate, prostaglandin F2-alpha causing smooth muscle constriction) is strictly contraindicated in patients with asthma; and Misoprostol (prostaglandin E1) and tranexamic acid (TXA) can be used broadly, with TXA administered within 3 hours of birth.

What is the passing score and honors cutoff for the OB/GYN shelf?

The NBME provides standardized equated percent correct scores, but grading thresholds are determined independently by each medical school’s clerkship committee. The national passing standard usually falls near the 5th to 10th percentile (typically an Equated Percent Correct around 62–65), while an Honors grade generally demands scoring at or above the 70th to 85th percentile (typically a scaled score between 79 and 84). Check your school’s rotation syllabus at the start of the clerkship to confirm your specific institutional target.

How do I distinguish placenta previa from placental abruption on test questions?

Look at pain and maternal vitals: Placenta previa presents with painless, bright red third-trimester vaginal bleeding in a relaxed, non-tender uterus; digital cervical examination is strictly contraindicated, and ultrasound confirms placental tissue covering the internal cervical os. Placental abruption presents with sudden, painful vaginal bleeding (or concealed retroplacental hemorrhage), hypertonic frequent uterine contractions, uterine tenderness, and fetal decelerations, commonly triggered by maternal hypertension, cocaine use, or abdominal trauma.

How is the OB/GYN shelf different from Step 2 CK women’s health questions?

Step 2 CK emphasizes general outpatient screening, routine prenatal labs, and non-emergent gynecologic pathology. In contrast, the NBME OB/GYN Subject Examination tests intrapartum management at a far more granular level: exact dilation arrest criteria (lack of progress for ≥ 4 hours with adequate contractions or ≥ 6 hours with inadequate contractions while on oxytocin), operative vaginal delivery prerequisites (forceps vs. vacuum), and specific surgical indications for gynecologic oncology staging.

OB/GYN Shelf Practice Questions: Labor Triage & Clerkship Strategy

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These ob-gyn shelf practice questions focus on electronic fetal monitoring, hypertensive emergencies of pregnancy, and postpartum hemorrhage protocols. Free includes 10 questions per day with the diagnostic; Pro is $180/yr ($15/mo billed yearly or $25/mo monthly).

By Jed Whetten, MD Candidate, University of Arizona College of Medicine – Phoenix.

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Worked Clinical Vignettes

Work through authentic cases from the Penziv item bank. Each question illustrates a high-yield clinical dilemma tested on the NBME Obstetrics and Gynecology Subject Examination.

Case 1: Electronic Fetal Monitoring: Late Decelerations & Uteroplacental Flow

A 31-year-old primigravida at 41 weeks of gestation is admitted to the labor and delivery unit in active labor. Cervical examination shows 6 cm dilation, 80% effacement, and 0 station. Tocodynamometry shows uterine contractions occurring every 2 to 3 minutes, lasting 60 seconds. Continuous electronic fetal monitoring reveals a baseline fetal heart rate of 140/min with moderate variability. Over the last 40 minutes, gradual, smooth decreases in the fetal heart rate begin after the peak of each uterine contraction and return to baseline well after the contraction has ended. Which of the following is the most likely underlying mechanism of these fetal heart rate findings?

Umbilical cord compression

Uteroplacental insufficiency— Correct Answer

Fetal head compression

Maternal hypotension causing autonomic reflex

Fetal cardiac conduction abnormality

Explanation:

Late decelerations are symmetric, gradual decreases in fetal heart rate with a nadir occurring after the contraction peak; they are caused by fetal hypoxemia secondary to uteroplacental insufficiency.

The electronic fetal monitoring tracing demonstrates late decelerations: gradual decreases in fetal heart rate (onset to nadir >= 30 seconds) that are delayed in timing relative to uterine contractions (nadir occurs after the peak of the contraction).
During a uterine contraction, myometrial compression transiently impedes placental intervillous perfusion. When baseline placental function is compromised (as in post-term pregnancy, maternal vascular disease, or abruption), transient fetal hypoxemia stimulates chemoreceptors, triggering a vagally mediated slowing of the fetal heart rate.
Therefore, late decelerations reflect uteroplacental insufficiency and warrant intrauterine resuscitative measures (e.g., maternal repositioning, intravenous fluid bolus, oxygen administration, reduction of uterotonic agents).

Late decelerations = uteroplacental insufficiency (hypoxia/acidemia).
Early decelerations = fetal head compression (vagal reflex; benign).
Variable decelerations = umbilical cord compression.

Case 2: Preeclampsia with Severe Features & Magnesium Neuroprotection

A 29-year-old primigravida at 35 weeks of gestation presents to the obstetric triage unit with a persistent throbbing frontal headache and blurry vision for the past 6 hours. She reports no epigastric pain or vaginal bleeding. Her blood pressure is 168/112 mm Hg and pulse is 84/min. Physical examination reveals 3+ bilateral patellar reflexes with two beats of ankle clonus. Urinalysis reveals 3+ protein. Platelet count is 145,000/mm3, serum creatinine is 0.8 mg/dL, AST is 28 U/L, and ALT is 24 U/L. Fetal heart rate tracing is reassuring (Category I). Which of the following is the most appropriate next step in management to prevent maternal seizures?

Intravenous lorazepam

Intravenous magnesium sulfate— Correct Answer

Intravenous phenytoin

Oral levetiracetam

Oral labetalol monotherapy

Explanation:

Intravenous magnesium sulfate is the drug of choice for the prevention and treatment of eclamptic seizures in patients with preeclampsia with severe features.

The patient meets criteria for preeclampsia with severe features based on severe range hypertension (systolic BP >=160 mm Hg or diastolic BP >=110 mm Hg on two occasions or once with neurological symptoms) and persistent neurological symptoms (frontal headache, visual changes, hyperreflexia, clonus).
The primary goal in reducing maternal morbidity in this setting is the prevention of eclampsia (tonic-clonic seizures).
Intravenous magnesium sulfate acts as a central neuroprotective agent, blocking N-methyl-D-aspartate (NMDA) receptors, promoting cerebral vasodilation, and dampening neuromuscular transmission; extensive randomized trials (e.g., Magpie Trial) have established it as superior to conventional anticonvulsants.

First-line seizure prophylaxis for preeclampsia with severe features is intravenous magnesium sulfate.
Therapeutic monitoring involves checking deep tendon reflexes, respiratory rate (>=12/min), and urine output (>=30 mL/hr) to guard against hypermagnesemia.
Calcium gluconate is the antidote for magnesium toxicity.

Case 3: Postpartum Hemorrhage & Stepwise Uterotonic Pharmacotherapy

A 34-year-old gravida 4, para 3, delivers a vigorous 4,200 g (9 lb 4 oz) male infant via uncomplicated spontaneous vaginal delivery after a prolonged second stage of labor. Fifteen minutes following delivery of an intact placenta, brisk continuous vaginal bleeding is noted. Estimated cumulative blood loss is 850 mL. Blood pressure is 92/58 mm Hg and pulse is 114/min. Abdominal examination reveals a soft, boggy uterus palpated 3 cm above the umbilicus. Bimanual uterine massage is immediately initiated while large-bore intravenous access and fluid resuscitation are established. Which of the following is the most appropriate initial pharmacologic therapy?

Sublingual misoprostol

Intramuscular carboprost tromethamine

Intravenous oxytocin— Correct Answer

Intravenous tranexamic acid

Intramuscular methylergonovine

Explanation:

Uterine atony is the most common cause of postpartum hemorrhage, and intravenous oxytocin administered concurrently with bimanual uterine massage is the first-line pharmacologic treatment.

The patient has postpartum hemorrhage (cumulative blood loss >= 1,000 mL or bleeding associated with hemodynamic instability) accompanied by tachycardia and hypotension.
Palpation of an enlarged, soft, and boggy uterus above the umbilicus confirms uterine atony as the underlying etiology, predisposed by fetal macrosomia (4,200 g), multiparity (G4P3), and prolonged labor.
The initial management is mechanical bimanual compression combined immediately with intravenous oxytocin infusion to stimulate rhythmic myometrial contractions and compress open spiral arterioles.

Uterine atony accounts for 70-80% of postpartum hemorrhage cases.
First-line therapy: Bimanual uterine massage + IV oxytocin.
Second-line uterotonics include methylergonovine (contraindicated in hypertension), carboprost tromethamine (contraindicated in asthma), and misoprostol.

Case 4: Recurrent Variable Decelerations & Intrauterine Amnioinfusion

A 25-year-old primigravida at 39 weeks of gestation is in the active phase of labor. Her cervix is dilated to 7 cm with 90% effacement, and the vertex is at -1 station. Spontaneous rupture of membranes occurred 2 hours ago with clear amniotic fluid. Continuous electronic fetal monitoring shows a baseline heart rate of 135/min with moderate variability. Over the past 30 minutes, there are recurrent, abrupt decreases in the fetal heart rate from the baseline to 85/min, lasting 45 seconds, with onset to nadir occurring in less than 15 seconds. The nadir and duration vary with each contraction. Maternal repositioning to the left lateral decubitus position and oxygen administration do not improve the tracing. Which of the following is the most appropriate next step in management?

Intrauterine amnioinfusion— Correct Answer

Intravenous terbutaline administration

Immediate cesarean delivery

Immediate artificial rupture of membranes

Emergent operative vaginal delivery with forceps

Explanation:

Amnioinfusion is indicated to relieve recurrent, persistent variable decelerations caused by umbilical cord compression in the setting of ruptured membranes.

The electronic fetal monitoring tracing reveals recurrent variable decelerations (abrupt drops in FHR >=15/min lasting >=15 seconds to <2 minutes, with onset to nadir <30 seconds).
Variable decelerations occur due to transient compression of the umbilical cord, which commonly worsens after membrane rupture due to oligohydramnios.
Initial management includes conservative measures: maternal repositioning (e.g., left or right lateral, knee-chest) to relieve cord entrapment. When variable decelerations persist despite repositioning, amnioinfusion (instillation of warm normal saline via an intrauterine pressure catheter) cushions the umbilical cord, significantly decreasing deceleration frequency and reducing the need for emergency cesarean section.

Variable decelerations = umbilical cord compression.
Initial step: Maternal repositioning.
Refractory recurrent variables with ruptured membranes: Amnioinfusion.
Cesarean delivery is reserved for Category III tracings or persistent non-reassuring status refractory to intrauterine resuscitation.

Case 5: Third-Trimester Painless Vaginal Bleeding & Placenta Previa

A 32-year-old gravida 2, para 1, at 36 weeks of gestation presents to labor and delivery with sudden-onset, painless, bright red vaginal bleeding that began 1 hour ago. She reports normal fetal movement and denies contractions or abdominal pain. Vital signs are: blood pressure 114/72 mm Hg, pulse 76/min, respirations 16/min, and temperature 36.8 C (98.2 F). Physical examination reveals a soft, non-tender, relaxed uterus with fundal height consistent with gestational age. Continuous external fetal monitoring reveals a baseline heart rate of 145/min with moderate variability and no decelerations. Tocodynamometry shows no uterine contractions. A sterile speculum examination confirms moderate active bleeding from the external cervical os. Which of the following is the most appropriate next diagnostic step?

Emergent exploratory laparotomy

Transabdominal followed by transvaginal ultrasound— Correct Answer

Amniocentesis for fetal lung maturity

Kleihauer-Betke test

Digital cervical examination

Explanation:

Painless third-trimester vaginal bleeding is highly suspicious for placenta previa; digital cervical examination is strictly contraindicated until placental location is confirmed via transabdominal and transvaginal ultrasonography.

The clinical presentation of sudden-onset, painless, bright red bleeding in the third trimester with a soft, non-tender uterus and reassuring fetal status is prototypical for placenta previa.
Digital cervical examination can disrupt placental attachment over the internal cervical os, precipitating catastrophic, life-threatening maternal hemorrhage.
The standard of care is immediate ultrasound evaluation (transabdominal followed by transvaginal ultrasound, which is safe and has near 100% sensitivity) to delineate the relationship of the placental margin to the internal os.

Painless third-trimester bleeding = Placenta previa (until proven otherwise).
Painful third-trimester bleeding + hypertonic/tender uterus = Placental abruption.
Never perform a digital cervical examination on a patient with third-trimester bleeding before ruling out placenta previa by ultrasound.

Core Decision Pillars for OB/GYN

High-yield decision rules for electronic fetal monitoring, hypertensive emergencies, and postpartum hemorrhage.

1. Electronic Fetal Heart Rate Tracing Interpretation

NICHD 3-tier categorization dictates management on labor and delivery. Category I tracings are reassuring and managed expectantly. Category III tracings (absent variability with recurrent late or variable decelerations, or sinusoidal pattern) demand immediate intrauterine resuscitation and preparation for urgent delivery. Category II tracings require close surveillance and correction of underlying triggers.

2. Hypertensive Disorders & Seizure Prophylaxis

Preeclampsia with severe features (systolic BP ≥ 160 mm Hg, diastolic BP ≥ 110 mm Hg, thrombocytopenia, elevated transaminases, pulmonary edema, or visual/neurological disturbances) requires immediate maternal seizure prophylaxis with intravenous magnesium sulfate. Antihypertensive therapy (IV labetalol, IV hydralazine, or oral nifedipine) is titrated to prevent maternal cerebrovascular complications.

3. Postpartum Hemorrhage Pharmacologic Algorithm

Uterine atony is the leading cause of postpartum hemorrhage. First-line therapy is concurrent bimanual uterine massage and intravenous oxytocin. Know the specific contraindications for second-line uterotonics: methylergonovine is strictly contraindicated in gestational hypertension or preeclampsia, while carboprost tromethamine is contraindicated in asthma.

Frequently Asked Questions

Common questions about shelf question volume, fetal monitoring tracings, and uterotonic contraindications.

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