Maternal Medical Complications of Pregnancy
Core concepts
The candidate must be fluent in how pregnancy alters physiology and how that alteration changes the diagnosis and management of chronic disease. Know the hemodynamic changes of pregnancy (30–50% plasma volume expansion, dilutional anemia, fall in systemic vascular resistance, increased cardiac output), the hypercoagulable state, and the renal changes (increased GFR, lower normal creatinine, glucosuria/proteinuria thresholds).
Hypertensive disease is high-yield: distinguish chronic hypertension, gestational hypertension, preeclampsia with and without severe features, superimposed preeclampsia, and eclampsia. Know the severe-feature criteria and the role of aspirin prophylaxis in high-risk patients. Diabetes requires understanding of screening thresholds, A1c limitations in pregnancy, and fetal surveillance implications of poor control. Cardiac disease questions hinge on lesion-specific tolerance and the timing of highest risk (second-to-third trimester transition and peripartum). Thyroid disease, epilepsy, SLE/APS, and thromboembolic disease each have pregnancy-specific traps.
Traps
- Treating a creatinine of 1.0 mg/dL as normal in pregnancy (it may already represent renal impairment).
- Missing that preeclampsia can present postpartum, up to 6 weeks.
- Assuming all anti-epileptics are equally teratogenic; valproate carries the highest risk.
- Confusing physiologic dyspnea with pathologic dyspnea; pregnancy does not cause resting hypoxemia.
- Forgetting that warfarin is contraindicated but low-molecular-weight heparin is preferred for mechanical valves in many protocols.
Rule of thumb
For any chronic disease, ask three questions: does pregnancy change the disease, does the disease change pregnancy outcomes, and does the medication need to change? Answer all three before choosing management.
Worked example: A woman with chronic hypertension on lisinopril conceives. The ACE inhibitor is discontinued (fetotoxicity), she is transitioned to a pregnancy-compatible agent, and baseline labs plus urine protein are obtained early because superimposed preeclampsia risk is high.