Master Obstetrics & Gynecology
for USMLE Step 2 CK

Core Concepts

Obstetrics & Gynecology (OB/GYN) encompasses women's reproductive health, pregnancy, childbirth, and postpartum care. Key principles include understanding the female endocrine axis (hypothalamic-pituitary-ovarian), menstrual cycle physiology, contraception, and the diagnosis/management of common benign and malignant conditions affecting the reproductive system. Pregnancy involves profound physiological changes, and meticulous antepartum, intrapartum, and postpartum care is essential to ensure maternal and fetal well-being. High-yield topics often involve critical pregnancy complications, gynecologic infections, cancer screening, and management of abnormal uterine bleeding.

Clinical Presentation

• **Ectopic Pregnancy**: Amenorrhea, unilateral pelvic pain, vaginal bleeding; shoulder pain (diaphragmatic irritation).
• **Preeclampsia**: Hypertension (BP ≥140/90 after 20 weeks) + proteinuria or signs of end-organ damage (headache, visual changes, RUQ pain).
• **Placenta Previa**: Painless vaginal bleeding, typically bright red, in the 2nd/3rd trimester.
• **Placental Abruption**: Painful vaginal bleeding, sudden onset, uterine tenderness/hypertonus, fetal distress.
• **Preterm Labor**: Regular uterine contractions causing cervical change before 37 weeks gestation.
• **PPROM**: Gush or leakage of clear/straw-colored fluid from the vagina, absence of labor.
• **Shoulder Dystocia**: Fetal head retracts against the perineum ("turtle sign") after crowning.
• **Postpartum Hemorrhage**: Excessive vaginal bleeding (>500mL for vaginal, >1000mL for C-section within 24 hours post-delivery).
• **Pelvic Inflammatory Disease (PID)**: Lower abdominal pain, fever, cervical motion tenderness, purulent cervical discharge.
• **Endometriosis**: Dysmenorrhea, chronic pelvic pain, dyspareunia, infertility.
• **Uterine Fibroids (Leiomyomas)**: Heavy menstrual bleeding, prolonged periods, pelvic pressure/bulk symptoms.
• **Polycystic Ovary Syndrome (PCOS)**: Oligo/amenorrhea, hirsutism, acne, central obesity, infertility.
• **Ovarian Torsion**: Sudden onset, severe, unilateral lower abdominal/pelvic pain, often with nausea/vomiting.
• **Endometrial Cancer**: Postmenopausal vaginal bleeding (most common symptom).
• **Cervical Cancer**: Postcoital bleeding, abnormal vaginal discharge (often asymptomatic early).

Diagnosis (Gold Standard)

**Pregnancy**: Serum or urine Beta-hCG (confirmation); Transvaginal ultrasound (TVUS) for viability and location (intrauterine vs. ectopic).
**Ectopic Pregnancy**: TVUS showing no intrauterine pregnancy with hCG above discriminative zone (~1500-2000 mIU/mL).
**Preeclampsia**: Clinical diagnosis with lab confirmation (e.g., 24hr urine protein >300mg or protein/creatinine ratio ≥0.3).
**Placenta Previa**: Transabdominal ultrasound.
**Placental Abruption**: Clinical diagnosis (US may show retroplacental hematoma but is not definitive).
**Preterm Labor**: Clinical (contractions + cervical change); Fetal fibronectin (fFN) for prediction in ambiguous cases.
**PPROM**: Nitrazine paper (turns blue), ferning pattern on microscopy, pooling of fluid in posterior fornix.
**PID**: Clinical triad (lower abdominal pain, cervical motion tenderness, adnexal tenderness). Laparoscopy is definitive but rarely necessary.
**Endometriosis**: Laparoscopy with biopsy.
**Uterine Fibroids**: Pelvic ultrasound.
**PCOS**: Rotterdam criteria (2 of 3: oligo/anovulation, clinical/biochemical hyperandrogenism, polycystic ovaries on US) after excluding other causes.
**Ovarian Torsion**: Laparoscopy (diagnostic and therapeutic). Doppler ultrasound may show decreased flow but normal flow doesn't rule out.
**Endometrial Cancer**: Endometrial biopsy or D&C.
**Cervical Cancer**: Colposcopy with directed biopsy.

Management (First Line)

**Ectopic Pregnancy**: Hemodynamically stable: Methotrexate. Unstable or contraindications: Laparoscopic salpingostomy/salpingectomy.
**Preeclampsia**: Delivery (definitive cure). MgSO4 for seizure prophylaxis. Antihypertensives (Labetalol, Hydralazine, Nifedipine).
**Placenta Previa**: Expectant management, no vaginal exams, planned C-section. Blood products readily available.
**Placental Abruption**: Stabilize mother (IV fluids, blood products), prompt delivery (C-section for fetal distress, vaginal if stable and progressing).
**Preterm Labor**: Tocolytics (Nifedipine, Indomethacin) to delay delivery. Corticosteroids (Betamethasone) for fetal lung maturity. MgSO4 for neuroprotection (<32 weeks).
**PPROM**: Hospitalization, antibiotics (ampicillin/amoxicillin + azithromycin), corticosteroids. Delivery if infection or fetal compromise.
**Shoulder Dystocia**: HELPERR mnemonic (Help, Episiotomy, Legs hyperflexed/McRoberts, External pressure/Suprapubic, Rotate/Woods screw, Remove posterior arm, Roll patient).
**Postpartum Hemorrhage**: Uterine massage, Oxytocin. Other uterotonics (Methylergonovine, Carboprost, Misoprostol).
**PID**: Outpatient: Ceftriaxone IM + Doxycycline PO ± Metronidazole PO. Inpatient for severe cases/pregnancy.
**Endometriosis**: NSAIDs, OCPs, GnRH agonists/antagonists, surgical excision.
**Uterine Fibroids**: Symptomatic: NSAIDs, OCPs, tranexamic acid. Definitive: Myomectomy (fertility desired) or Hysterectomy.
**PCOS**: Lifestyle modification (weight loss), OCPs (menstrual regulation, hirsutism), Metformin (insulin resistance), Clomiphene (infertility).
**Ovarian Torsion**: Laparoscopic detorsion and oophoropexy.
**Endometrial Cancer**: Total hysterectomy with bilateral salpingo-oophorectomy; +/- lymphadenectomy, radiation, chemotherapy depending on stage.
**Cervical Cancer**: LEEP/conization for early stage, radical hysterectomy/radiation/chemo for advanced.

Exam Red Flags