Master Obstetrics & Gynecology
for USMLE Step 2 CK

What the USMLE Step 2 CK Tests in Obstetrics & Gynecology

Obstetrics & Gynecology on USMLE Step 2 CK tests the candidate's ability to manage common obstetric emergencies, antenatal screening, intrapartum decision-making, and gynecologic presentations such as abnormal uterine bleeding, pelvic pain, and menopause. Emphasis is on recognizing when to intervene (e.g., preeclampsia with severe features, shoulder dystocia, ectopic pregnancy), selecting appropriate first-line treatments (e.g., magnesium sulfate for eclampsia, methotrexate for unruptured ectopic), and applying evidence-based screening guidelines (e.g., GBS prophylaxis, gestational diabetes screening, cervical cancer screening). Candidates must be fluent in diagnostic criteria (e.g., Bishop score, FIGO staging for endometrial cancer) and know when to consult or operate. The exam prioritizes management over pathophysiology, with many questions presenting a clinical vignette requiring a next best step in diagnosis or treatment.

High-Yield Concepts

• Preeclampsia with Severe Features: Diagnose when BP ≥160/110 mmHg plus proteinuria or end-organ dysfunction (thrombocytopenia, elevated LFTs, renal insufficiency, pulmonary edema, cerebral/visual symptoms). First-line management: IV labetalol or hydralazine for acute hypertension, IV magnesium sulfate for seizure prophylaxis. Delivery is definitive treatment; timing depends on gestational age (≥34 weeks: deliver; <34 weeks: consider corticosteroids and expectant management only if stable).
• Shoulder Dystocia: Recognize by turtle sign (head retraction) after delivery of the fetal head. Immediate steps: call for help, McRoberts maneuver (hyperflex maternal thighs) plus suprapubic pressure (NOT fundal pressure). If unsuccessful, proceed to Woods corkscrew, Rubin maneuver, or delivery of posterior arm. Document all maneuvers and neonatal outcomes (brachial plexus injury, clavicle fracture).
• Group B Streptococcus (GBS) Prophylaxis: Screen all pregnant women at 35–37 weeks with rectovaginal swab. Intrapartum IV penicillin G (5 million units loading, then 2.5 million units q4h) or ampicillin (2g loading, then 1g q4h) if GBS-positive, or if risk factors: preterm labor <37 weeks, ROM ≥18 hours, or intrapartum fever ≥38°C. For penicillin allergy: cefazolin if low risk; clindamycin or vancomycin if high risk (after susceptibility testing).
• Ectopic Pregnancy Diagnosis and Management: Suspect in first-trimester vaginal bleeding with adnexal pain; key findings: quantitative β-hCG >1500 IU/L with no intrauterine pregnancy on transvaginal ultrasound, or empty uterus with adnexal mass. First-line stable: laparoscopic salpingostomy (if desire fertility) or salpingectomy; medical: methotrexate (single-dose 50 mg/m² IM) if unruptured, mass <3.5 cm, no fetal cardiac activity, and reliable patient. Ruptured ectopic requires emergency laparotomy.
• Abnormal Uterine Bleeding (PALM-COEIN Classification): Classify using PALM-COEIN: structural (polyp, adenomyosis, leiomyoma, malignancy) and non-structural (coagulopathy, ovulatory dysfunction, endometrial, iatrogenic, not yet classified). First-line for heavy menstrual bleeding without structural cause: tranexamic acid or NSAIDs (mefenamic acid), or levonorgestrel IUD. For anovulatory bleeding (e.g., PCOS): cyclic progestins or combined oral contraceptive. Endometrial biopsy indicated if age >45 or risk factors (obesity, Lynch syndrome).
• Gestational Diabetes Mellitus (GDM) Diagnosis and Management: Screen at 24–28 weeks with 75g OGTT; diagnose if any one value: fasting ≥5.1 mmol/L (92 mg/dL), 1-hour ≥10.0 mmol/L (180 mg/dL), 2-hour ≥8.5 mmol/L (153 mg/dL). First-line management: medical nutrition therapy and glucose monitoring (fasting <5.3, 1-hour postprandial <7.8 mmol/L). If targets not met, start metformin or insulin (NPH or rapid-acting analogs). Postpartum: re-screen with 75g OGTT at 6–12 weeks.
• Ovarian Torsion: Present with acute unilateral pelvic pain, nausea, vomiting, and an adnexal mass on ultrasound with absent or reduced ovarian arterial/venous Doppler flow. Emergency management: laparoscopic detorsion (ovarian conservation preferred in reproductive-age women). Do not delay for imaging if high suspicion; time to surgery <36 hours improves ovarian salvage. Oophorectomy indicated only if frankly necrotic.
• Cervical Cancer Screening (US Guidelines): Start at age 21. Ages 21–29: cytology alone every 3 years. Ages 30–65: cytology + HPV co-testing every 5 years (preferred) or cytology alone every 3 years. Discontinue after age 65 if adequate prior negative screens (three consecutive negative cytology or two negative co-tests within 10 years). Abnormal results: ASC-US with high-risk HPV → colposcopy; LSIL → colposcopy if age ≥25; HSIL → colposcopy with biopsy. HPV vaccination (Gardasil 9) recommended for ages 9–26.

Common Traps in Obstetrics & Gynecology Questions

• Confusing preeclampsia with gestational hypertension: preeclampsia requires proteinuria or end-organ dysfunction, not just elevated BP.
• Using fundal pressure in shoulder dystocia—this is contraindicated and increases risk of brachial plexus injury.
• Assuming a patient with first-trimester bleeding and a positive β-hCG has a viable intrauterine pregnancy without confirming with ultrasound; ectopic must be excluded.
• Treating anovulatory bleeding with estrogen alone in a woman with intact uterus—this increases endometrial cancer risk; always add progestin.
• Ordering a glucose tolerance test in a woman with fasting glucose ≥7.0 mmol/L (126 mg/dL) or random ≥11.1 mmol/L (200 mg/dL)—this is diagnostic of overt diabetes, not GDM.
• Forgetting to screen for GBS in preterm labor or ROM ≥18 hours if GBS status unknown—prophylaxis is indicated regardless of prior screening.

How to Revise Obstetrics & Gynecology for the USMLE Step 2 CK

On USMLE Step 2 CK, Obstetrics & Gynecology questions are heavily weighted toward management decisions in acute settings (e.g., postpartum hemorrhage, cord prolapse, ectopic rupture) and guideline-based screening/ prevention (GBS, cervical cancer, GDM). Many vignettes are framed as 'next best step' or 'most appropriate initial management', requiring you to distinguish between observation, medical therapy, and surgical intervention. Prioritize memorizing cut-off values (e.g., BP thresholds, β-hCG discriminatory zone, Bishop score components), first-line drugs with doses (e.g., oxytocin, misoprostol, magnesium sulfate), and indications for operative delivery. Practice interpreting ultrasound reports and fetal heart tracings (category I, II, III). Do not waste time on rare genetic syndromes; focus on common presentations like preeclampsia, ectopic, and abnormal bleeding. Use a systematic approach: stabilize, diagnose, then treat.

Practise it: MedLumen has 50 Obstetrics & Gynecology questions for the USMLE Step 2 CK, each with a full explanation and references.