System 08 · ~10% of exam
OB / Gyn
Pregnancy changes everything. Always check hCG. Key threads: bleeding (age-stratified), pelvic pain (pregnant vs not), pregnancy complications (HTN, DM, infection), prenatal screening.
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Chief complaints
BUILD THE DIFFERENTIAL
Vignettes enter through one of these doors. Each complaint lays out the full differential, marks the can't-miss diagnoses, and tells you the next right action for each.
CHIEF COMPLAINT · HIGH-YIELD
Vaginal bleeding
Pregnant or not? Age stratifies the differential.
Approach
First step is always pregnancy test. In pregnancy: ectopic, threatened or complete abortion, molar, placenta previa or abruption (later). Non-pregnant: anovulation (PCOS), structural (fibroids, polyps, adenomyosis), malignancy (endometrial after 45), bleeding disorders in young.
The differential
| Diagnosis | Key features / clues | Next step |
|---|---|---|
| Ectopic pregnancy | Reproductive age woman, amenorrhea, vaginal bleeding, pelvic pain. Positive hCG. Risk factors: PID, prior ectopic, IVF, tubal surgery, IUD. | Transvaginal US · if unstable → OR. If stable and ruptured unlikely: methotrexate if eligible, or surgery |
| Placenta previa | Painless bright red bleeding in 3rd trimester. | NO digital exam · transabdominal or transvaginal US · if stable and preterm, expectant with strict pelvic rest · delivery by C-section at 36–37 weeks |
| Placental abruption | Painful dark bleeding in 3rd trimester, tender rigid uterus, fetal distress. Risk factors: HTN, trauma, cocaine, prior abruption. | Continuous fetal monitoring · fluids · expedite delivery (usually C-section if fetal distress) |
| Threatened abortion | Bleeding in 1st trimester, closed cervix, viable pregnancy. | Expectant management · reassurance |
| Miscarriage / incomplete abortion | Open cervix, products of conception visible or passing. | Expectant vs medical (misoprostol) vs surgical (D&C) |
| Molar pregnancy | Markedly elevated hCG, hyperemesis, preeclampsia in first half, snow-storm US, no fetal heartbeat. | D&C · follow hCG weekly to undetectable · contraception during surveillance |
| Endometrial cancer | Postmenopausal bleeding, or AUB > 45. | Transvaginal US (endometrial stripe > 4 mm post-menopause) · endometrial biopsy |
| Fibroids | Heavy menstrual bleeding, bulk symptoms. | Pelvic exam, transvaginal US · medical (OCPs, IUD, GnRH agonists) or surgical (myomectomy, UAE, hysterectomy) |
| Anovulatory bleeding / PCOS | Adolescent or perimenopausal, irregular cycles. | CBC, TSH, hCG, prolactin · combined OCPs or cyclic progesterone |
⚑ = can't-miss diagnosis · rule out first
Classic vignette
Exam-style stem
A 26-year-old woman with 7 weeks of amenorrhea presents with right lower quadrant pain and vaginal spotting. hCG 2800. Transvaginal US: no intrauterine pregnancy, 2 cm right adnexal mass, free fluid in pelvis.
Next step?
Answer › Ectopic pregnancy. Transvaginal US with no IUP and hCG above discriminatory zone (1500–2000) is diagnostic. If stable and meets criteria (unruptured, < 3.5 cm, hCG < 5000, no heartbeat, reliable follow-up): methotrexate. Otherwise: laparoscopic salpingostomy or salpingectomy.
Pearls
Pearl
Rh-negative women with any bleeding in pregnancy get RhoGAM (anti-D immune globulin).
Pearl
Placenta previa: painless bleeding, no digital exam until US confirms location. Abruption: painful bleeding, uterine tenderness, fetal distress.
Pearl
Postmenopausal bleeding is endometrial cancer until proven otherwise. Endometrial biopsy.
CHIEF COMPLAINT · HIGH-YIELD
Pelvic pain
Pregnant vs not. Acute vs chronic. Gyn vs GI vs GU.
Approach
Pregnancy test first. Acute: ectopic, ovarian torsion, TOA, ruptured cyst, appendicitis, PID. Chronic: endometriosis, adhesions, fibroids, adenomyosis, IBS, interstitial cystitis.
The differential
| Diagnosis | Key features / clues | Next step |
|---|---|---|
| Ovarian torsion | Sudden severe unilateral pelvic pain with nausea, adnexal mass, absent Doppler flow on US. | Emergent laparoscopic detorsion (preserve ovary if possible) |
| Ectopic pregnancy | Reproductive age, positive hCG, pelvic pain. | Transvaginal US · management as above |
| Tubo-ovarian abscess | PID history, adnexal mass, fever, toxic appearance. | IV antibiotics (cefoxitin + doxycycline + metronidazole or clindamycin) · drainage if large or not responding |
| Pelvic inflammatory disease | Cervical motion tenderness, adnexal tenderness, fever, purulent discharge. Risk: young, multiple partners, STIs. | Treat empirically: ceftriaxone + doxycycline + metronidazole (outpatient) · admit if pregnant, failed outpatient, TOA |
| Endometriosis | Dysmenorrhea, dyspareunia, chronic pelvic pain, infertility. Classic 3 D's + infertility. | Clinical diagnosis · laparoscopy definitive · NSAIDs, OCPs, GnRH agonists, surgery |
| Ovarian cyst rupture | Sudden pain, often mid-cycle, free fluid. | Conservative management if stable |
⚑ = can't-miss diagnosis · rule out first
Classic vignette
Exam-style stem
A 22-year-old woman with 4 hours of sudden severe right pelvic pain and vomiting. US: enlarged right ovary (6 cm) with absent Doppler flow.
Most likely diagnosis and next step?
Answer › Ovarian torsion. Emergent laparoscopic detorsion. Do not remove the ovary if it appears viable after detorsion, it often recovers even if it looks dusky.
Pearls
Pearl
PID threshold for diagnosis is deliberately low: CMT, uterine, or adnexal tenderness in a sexually active woman is enough to treat empirically. Missing PID causes infertility.
Pearl
Fitz-Hugh-Curtis syndrome: perihepatitis from PID. RUQ pain with PID symptoms.
Pearl
Mittelschmerz: mid-cycle pelvic pain from ovulation, usually mild and self-limited.
CHIEF COMPLAINT · HIGH-YIELD
Pregnancy complaints
HTN in pregnancy is a spectrum. DM is screened at 24–28 weeks. GBS at 36–37.
Approach
Early pregnancy: hyperemesis, UTI, vaginal bleeding. Mid: HTN screening, diabetes screening, anatomy scan. Late: preeclampsia, preterm labor, PPROM, normal labor vs dystocia.
The differential
| Diagnosis | Key features / clues | Next step |
|---|---|---|
| Preeclampsia with severe features | BP ≥ 160/110, proteinuria, headache, visual changes, RUQ pain, thrombocytopenia, elevated LFTs, renal dysfunction, pulmonary edema. > 20 weeks. | IV labetalol or hydralazine · magnesium for seizure prophylaxis · delivery at 34 weeks (severe) or 37 weeks (without severe features) |
| Eclampsia | Preeclampsia + seizure. | Magnesium sulfate 4–6 g IV bolus then 2 g/hr · BP control · delivery after stabilization |
| HELLP syndrome | Hemolysis, Elevated LFTs, Low Platelets. RUQ pain. | Deliver · magnesium · transfuse as needed |
| Gestational diabetes | Screening 24–28 weeks with 1-hour 50g challenge (> 135–140). Confirm with 3-hour 100g OGTT. | Nutrition therapy · glucose monitoring · insulin or metformin if diet fails |
| Gestational hypertension | New HTN after 20 weeks without proteinuria or end-organ signs. | Serial BP · urine protein · deliver at 37 weeks |
| Chronic hypertension | HTN before 20 weeks or pre-pregnancy. | Labetalol, nifedipine, methyldopa · avoid ACEi/ARB |
| Hyperemesis gravidarum | Severe nausea/vomiting with dehydration, ketosis, weight loss > 5%. | IV fluids, antiemetics (pyridoxine + doxylamine first, then ondansetron, metoclopramide) |
| Preterm labor | Regular contractions with cervical change before 37 weeks. | < 34 wk: tocolytics (nifedipine or indomethacin), betamethasone for lung maturity, magnesium for neuroprotection if < 32 wk. GBS prophylaxis. 34–37 wk: betamethasone still indicated |
| PPROM | Rupture before 37 weeks and before labor. Nitrazine + positive, ferning, pooling. | Admit · antibiotics (ampicillin + azithromycin) · betamethasone if < 34 wk · deliver if chorio, fetal distress, or ≥ 34 wk |
⚑ = can't-miss diagnosis · rule out first
Classic vignette
Exam-style stem
A G1P0 at 34 weeks presents with headache and vision changes. BP 168/108. Urine protein 3+. Reflexes 3+. Platelets 90k. AST 120.
Management?
Answer › Preeclampsia with severe features and HELLP. Admit. IV labetalol for BP < 160/110. Magnesium sulfate for seizure prophylaxis. Delivery indicated (severe features at > 34 weeks and HELLP). Betamethasone can be given but should not delay delivery.
Pearls
Pearl
Magnesium toxicity: hyporeflexia (first sign), respiratory depression, cardiac arrest. Antidote is calcium gluconate.
Pearl
Preeclampsia prophylaxis: low-dose aspirin from 12 weeks for high-risk patients (prior preeclampsia, chronic HTN, DM, multiple gestation, autoimmune).
Pearl
Rh-negative mom gets RhoGAM at 28 weeks and within 72 hours of delivery if baby is Rh-positive.
CHIEF COMPLAINT
Amenorrhea
Pregnancy first. Then structural, ovarian, pituitary, hypothalamic.
Approach
Primary: no menses by 15 with normal puberty, or 13 without. Secondary: 3 cycles or 6 months without menses. Workup: pregnancy test, TSH, prolactin, FSH/LH, estradiol. Progesterone challenge if estrogen status unclear.
The differential
| Diagnosis | Key features / clues | Next step |
|---|---|---|
| Pregnancy | Reproductive age. | hCG |
| PCOS | Oligo/amenorrhea, hyperandrogenism, polycystic ovaries (2 of 3 Rotterdam criteria). | Labs · OCPs for menstrual regulation · metformin · spironolactone · lifestyle |
| Premature ovarian insufficiency | Amenorrhea < 40, hot flashes, elevated FSH. | FSH × 2 separated by 1 month · karyotype if young · hormone replacement |
| Hyperprolactinemia | Galactorrhea, amenorrhea. Medications (antipsychotics), prolactinoma, hypothyroidism. | Prolactin · TSH · MRI pituitary if persistently elevated · dopamine agonist (cabergoline) |
| Functional hypothalamic amenorrhea | Low body weight, excessive exercise, stress. Low FSH/LH/estradiol. | Weight restoration · reduce exercise · nutritional counseling |
| Asherman syndrome | Secondary amenorrhea after D&C or endometritis. | Hysteroscopy with adhesion lysis |
⚑ = can't-miss diagnosis · rule out first
Pearls
Pearl
Primary amenorrhea with breast development but no uterus: Mullerian agenesis or complete androgen insensitivity. Karyotype differentiates.
Pearl
Turner syndrome: short stature, webbed neck, primary amenorrhea, streak ovaries, cardiac (bicuspid AV, coarctation). 45,XO.
Pearl
Hyperprolactinemia can be from antipsychotics, antiemetics (metoclopramide), estrogens, TCAs. Always medication review first.
✦
Disease deep dives
DEFINITIVE DX
Once you've identified the likely diagnosis from the chief complaint, these pages give you the presentation, workup, management, and exam pearls in depth.
Preeclampsia
New HTN + end-organ damage after 20 weeks. Magnesium for seizure prophylaxis. Delivery is cure.
Ectopic Pregnancy
Positive hCG with no IUP on transvaginal US at discriminatory zone. Methotrexate or surgery.
PCOS
Oligo/amenorrhea + hyperandrogenism + polycystic ovaries (Rotterdam: 2 of 3). Insulin resistance.
Uterine Fibroids
Most common pelvic tumor. Submucosal cause bleeding; subserosal cause bulk symptoms.
Cervical Cancer Screening
Pap + HPV co-testing drives guidelines. Updated recommendations emphasize HPV testing.
DISEASE DEEP DIVE
Preeclampsia
New HTN + end-organ damage after 20 weeks. Magnesium for seizure prophylaxis. Delivery is cure.
Presentation
Headache, visual changes, RUQ pain, edema. BP ≥ 140/90 or ≥ 160/110 (severe).
Workup
- BP. Two readings ≥ 4 hours apart. Severe range = ≥ 160/110.
- Urine protein. ≥ 300 mg/24 hr, spot urine protein/Cr ≥ 0.3, or dipstick ≥ 1+.
- End-organ workup. CBC (platelets), LFTs, Cr. Proteinuria not required if severe features present.
Management
- BP control. Labetalol, hydralazine, nifedipine. Target < 160/110.
- Seizure prophylaxis. Magnesium sulfate 4–6 g bolus then 1–2 g/hr. Continue through delivery and 24 hr postpartum.
- Delivery timing. Without severe features: deliver at 37 weeks. With severe features: deliver at 34 weeks (or immediately if unstable). Route depends on obstetric factors.
- Betamethasone. For lung maturity if preterm.
- Postpartum. Can present up to 6 weeks postpartum. Continue magnesium 24 hours after delivery.
Pearls
Pearl
Magnesium is seizure prophylaxis, not treatment. For active eclampsia: more magnesium, benzodiazepine, emergent delivery.
Pearl
Preeclampsia prevention: low-dose aspirin 81 mg from 12 weeks for high-risk patients (prior preeclampsia, chronic HTN, DM, multiple gestation, autoimmune, CKD).
Pearl
HELLP: hemolysis (schistocytes, LDH up, haptoglobin down), elevated liver enzymes, low platelets. RUQ pain is a red flag. Delivery indicated.
DISEASE DEEP DIVE
Ectopic Pregnancy
Positive hCG with no IUP on transvaginal US at discriminatory zone. Methotrexate or surgery.
Presentation
Amenorrhea, vaginal bleeding, unilateral pelvic pain. Ruptured: shoulder pain, syncope, peritoneal signs.
Workup
- hCG. Discriminatory zone 1500–2000. If hCG above this with no IUP, ectopic is likely.
- Transvaginal US. Look for IUP (gestational sac with yolk sac), adnexal mass, free fluid.
- Serial hCG. If hCG below discriminatory zone and no definitive IUP or ectopic, repeat in 48 hours. Normal IUP doubles every 48 hrs; ectopic or failed pregnancy rises abnormally or falls.
Management
- Unstable. OR immediately, salpingectomy or salpingostomy.
- Methotrexate eligibility. Unruptured, hemodynamically stable, hCG < 5000, no heartbeat, mass < 3.5 cm, reliable follow-up. No contraindications (liver disease, thrombocytopenia, immunosuppression, breastfeeding, sensitive organ dysfunction).
- Methotrexate follow-up. hCG on days 4 and 7. Should drop ≥ 15% between days 4 and 7. Continue weekly until undetectable.
- Surgery. For ruptured, contraindication to MTX, desiring sterilization, large mass, high hCG.
Pearls
Pearl
RhoGAM for all Rh-negative women with ectopic or miscarriage.
Pearl
Pregnancy of unknown location: positive hCG, no IUP, no ectopic seen. Serial hCG to follow. Trust the trend.
Pearl
Heterotopic pregnancy (simultaneous intrauterine and ectopic) is rare overall but more common with IVF. Do not assume a seen IUP rules out ectopic in ART patients.
DISEASE DEEP DIVE
PCOS
Oligo/amenorrhea + hyperandrogenism + polycystic ovaries (Rotterdam: 2 of 3). Insulin resistance.
Presentation
Irregular periods, hirsutism, acne, obesity, infertility, acanthosis nigricans.
Workup
- Labs. Elevated testosterone (mildly), LH:FSH > 2, normal or slightly low SHBG, elevated AMH. Rule out 21-hydroxylase deficiency (17-OHP), Cushing, thyroid, prolactin, acromegaly.
- Metabolic screening. OGTT, lipids, A1c. High risk for T2DM and cardiovascular disease.
- Pelvic US. Polycystic ovaries (12+ follicles per ovary or ovarian volume > 10 mL). Not required for diagnosis if other criteria met.
Management
- Lifestyle. Weight loss (5–10%), often restores ovulation.
- Menstrual regulation. Combined OCPs (first-line) or cyclic progesterone.
- Hirsutism. Spironolactone, finasteride, topical eflornithine. Takes 6+ months to see effect.
- Infertility. Letrozole first-line (better than clomiphene). Metformin adjunct.
- Metabolic. Metformin for insulin resistance. Screen and treat lipids, DM.
Pearls
Pearl
Unopposed estrogen (from anovulation) increases endometrial cancer risk. All PCOS patients need cyclic progesterone or OCPs even if not sexually active.
Pearl
Letrozole replaced clomiphene as first-line ovulation induction in PCOS. Higher live birth rate.
Pearl
PCOS: think lifelong metabolic disease, not just reproductive.
DISEASE DEEP DIVE
Uterine Fibroids
Most common pelvic tumor. Submucosal cause bleeding; subserosal cause bulk symptoms.
Presentation
Heavy menstrual bleeding, pelvic pressure, urinary frequency, dyspareunia, subfertility.
Workup
- Pelvic exam + US. Transvaginal or transabdominal. Characterize size and location.
- MRI. If considering surgery for mapping.
- CBC. Iron deficiency anemia from bleeding.
Management
- Asymptomatic. Observation.
- Medical. NSAIDs, tranexamic acid for bleeding. Levonorgestrel IUD. OCPs. GnRH agonists (temporizing, before surgery). GnRH antagonists + add-back estrogen (elagolix, relugolix).
- Surgical. Myomectomy (preserves fertility), uterine artery embolization, hysterectomy (definitive), endometrial ablation (select cases).
Pearls
Pearl
Degenerating fibroid in pregnancy can cause pain. Usually conservative management.
Pearl
Rapidly growing fibroid, especially postmenopausal, raises concern for leiomyosarcoma (rare).
DISEASE DEEP DIVE
Cervical Cancer Screening
Pap + HPV co-testing drives guidelines. Updated recommendations emphasize HPV testing.
Presentation
Screening in asymptomatic women. Symptomatic: post-coital bleeding, abnormal bleeding, discharge.
Workup
- Start at 21. Regardless of sexual history.
- 21–29. Pap every 3 years (cytology only).
- 30–65. Pap + HPV co-testing every 5 years (preferred), OR pap alone every 3, OR HPV alone every 5.
- Stop at 65. If adequate prior screening and no history of high-grade lesion or cancer.
Management
- ASCUS + HPV positive or LSIL. Colposcopy.
- HSIL or CIN2+. Colposcopy with biopsy. LEEP or cold knife cone if CIN2/3 confirmed.
- HPV vaccination. 9-valent (Gardasil 9). Ages 9–45. Most effective before sexual debut.
Pearls
Pearl
HPV 16 and 18 cause 70% of cervical cancers. Vaccine covers these plus 31, 33, 45, 52, 58 plus 6, 11 (warts).
Pearl
Post-hysterectomy (for benign reasons, no cervix): no further screening if no history of high-grade lesion.
Pearl
Pregnancy: colposcopy is safe. LEEP deferred until postpartum unless invasive cancer.