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USMLE Step 2 (Fach) / Obstetrics (Lektion)
- Fetal hydrops Pathogenesis:- ↑ cardiac output demand causing heart failure- ↑ fluid movement into interstitial spaces (third spacing) Clinical features:- Pericardial effusion- Pleural effusion- Ascites- Skin edema- Placental edema- Polyhydramnios Etiology:- Rh(D) alloimmunization- Parvovirus B19 infection- Fetal aneuploidy- Cardiovascular abnormalities- Thalassemia (e.g., hemoglobin Barts)
- Decelerations A temporary decline in the FHR of > 15 bpm for a maximum duration of 3 minutes Early deceleration:- Usually a normal reading (no fetal distress)- Causes: compression of the head during contraction triggers a vagal response Late deceleration:- Causes: uteroplacental insufficiency (leads to fetal hypoxia and acidosis)- Measures:→ Intrauterine resuscitation→ If FHR pattern does not improve despite intrauterine resuscitation → emergency c-section Variable deceleration:- Causes: Umbilical cord compression/prolapse - Measures→ If intermittent variable decelerations (< 50% of contractions): usually no interventions are needed→ If recurrent variable decelerations (≥ 50% of contractions): Intrauterine resuscitation→ If FHR pattern does not improve despite intrauterine resuscitation → emergency c-section Intrauterine resuscitation measures:- Repositioning of the mother, administer O2 and possibly fluids- If initial steps unsuccessful, consider:→ Amnioinfusion: instillation of saline into the amniotic cavity after artificial rupture of membranes→ If tachysystole is present (> 5 contractions in a period of 10 minutes): reduce uterine activity by giving tocolytics→ Emergency cesarean section
- Gestational age and date Naegele's rule: used to calculate the date of delivery (due date) = First day of the last menstrual period + 7 days + 1 year - 3 months Ultrasound: more accurate than Naegele's rule- Measurement of the crown-rump length (CRL) in the first trimester- Measurement of biparietal diameter, femur length, and abdominal circumference (starting at 14 weeks)
- Stillbirth (> 20 weeks' gestation) - Do not rush delivery unless maternal health is at risk (i.e., preeclampsia, infection). - Spontaneous labor usually begins within 2 weeks of intrauterine fetal death. However, labor may be induced with oxytocin if maternal disease develops (e.g., coagulation abnormalities) or if the patient prefers induction. - Vaginal delivery is safer than cesarean section, but many patients will prefer cesarean section. - Express empathy and acknowledge patient grief; provide privacy and emotional support. - Patients should be offered a fetal autopsy to determine the cause of death.
- Antiphospholipid syndrome Antiphospholipid syndrome (APS) is an autoimmune disease that increases the risk of thrombosis as a result of procoagulatory antibodies. Etiology:- Primary- Secondary: Systemic lupus erythematosus, rheumatoid arthritis, neoplasms, HIV, hepatitis A/B/C Clinical features:- Venous thrombosis: Deep vein thrombosis, pulmonary embolism- Livedo reticularis- Ulceration (see chronic venous insufficiency)- Arterial thrombosis: Stroke, transient ischemic attacks, ccclusion of organ arteries (e.g., myocardial infarction), occlusion of distal extremity arteries (ischemia and gangrene)- Pregnancy-related: recurrent miscarriages and premature births- Capillaries: splinter hemorrhages Diagnostics:- History of→ Arterial or venous thrombosis→ Recurrent miscarriages (≥ 1)- Serology for antiphospholipid antibodies→ Lupus anticoagulant (LA): leads to a prolonged aPTT (Mixing study, Russell viper venom test)→ Anticardiolipin antibodies (aCL) (IgG and IgM): patients with APS often test false positive for syphilis (positive VDRL or RPR), as the antigen used in syphilis tests is cardiolipin.→ Anti-β2-glycoprotein antibodies- Thrombocytopenia- Hemolysis, leukocytopenia Acute management:- SC low molecular weight heparin (LMWH) or IV unfractionated heparin- In severe cases: high-dose glucocorticoids, plasmapheresis, and/or immunoglobulins Secondary prophylaxis:- Low risk: low-dose aspirin- High risk, no desire to become pregnant: long-term treatment with oral warfarin- Wish to have children, prevention of miscarriage: LMWH + aspirin
- Blighted ovum Pregnancy in which the embryo never develops or develops and is reabsorbed Diagnostics:- Normal-appearing gestational sac- Absence of an embryo
- Pyelonephritis in pregnancy Risk factors:- Asymptomatic bacteriuria- Diabetes mellitus- Age < 20- Tobacco use Common pathogens:- E. coli- Klebsiella- Enterobacter- Group B Streptococcus Complications:- Preterm labor- Low birth weight- ARDS Treatment:- Intravenous antibiotics- Supportive therapy
- Retained placenta Definition: No placental expulsion within 30 minutes of infant delivery due to:- Placental detachment failure (adherens)- Morbid placental attachment (accreta)- Placental entrapment Risk factors:- Gestational age 24-27 weeks- Stillbirth- Placenta accreta- History of prior retained placenta Complications:- Postpartum hemorrhage- Endometritis Management:- Manual placenta extraction- Dilation & curettage
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