Reproductive · Year 2 · from Reproductive
Case 3: Physiologic Anemia of Pregnancy
Clinical Image
Source: Wikipedia - Pregnancy - CC BY-SA 4.0
Case Presentation
A 26-year-old G1P0 woman at 28 weeks gestation presents for routine prenatal care. She reports mild fatigue but is otherwise asymptomatic. She has been compliant with her prenatal vitamins. Physical examination reveals a soft systolic flow murmur (grade 2/6) and mild dependent edema, both noted at previous visits. Fundal height is appropriate for gestational age. Laboratory studies obtained as part of routine 28-week testing show hemoglobin 10.8 g/dL (down from 12.5 g/dL at her first prenatal visit), hematocrit 33%, MCV 94 fL (normal), MCH normal, and ferritin 35 ng/mL (adequate iron stores). The peripheral blood smear is unremarkable. Her complete metabolic panel and urinalysis are normal. The patient is reassured that her findings are consistent with physiologic anemia of pregnancy and do not represent true anemia requiring intervention. She is counseled about the cardiovascular adaptations of pregnancy, including the 40-50% expansion of plasma volume that exceeds the 20-30% increase in red blood cell mass, resulting in hemodilution. The mild decrease in hemoglobin is expected and actually beneficial for uteroplacental perfusion by reducing blood viscosity. No additional treatment beyond continued prenatal vitamins is recommended.
Key Learning Points
- Pregnancy causes a 40-50% increase in plasma volume but only a 20-30% increase in RBC mass, resulting in hemodilution and lower hemoglobin concentration
- Hemoglobin levels typically reach their nadir (approximately 11-12 g/dL) around 28-32 weeks gestation
- This "physiologic anemia" is beneficial, as reduced viscosity improves uteroplacental blood flow; hemoglobin <11 g/dL in the first trimester or <10.5 g/dL in the second trimester warrants investigation for true anemia
- Other normal cardiovascular changes include increased cardiac output (30-50%), decreased systemic vascular resistance, and innocent flow murmurs