Nutrient Transport from Mother to Fetus: The Placental Pathway

The placenta is the lifeline between mother and fetus, mediating all nutrient, gas, and waste exchange.

Step‑by‑Step Process

1. Maternal blood supply: Uterine arteries deliver oxygenated, nutrient‑rich blood to the intervillous space (maternal side).
2. Placental barrier: Chorionic villi (fetal capillaries) bathe in maternal blood; exchange occurs across the syncytiotrophoblast basement membrane and fetal capillary endothelium.
3. Transport mechanisms:
   • Passive diffusion: O₂, CO₂, lipid‑soluble substances.
   • Facilitated diffusion: Glucose (GLUT1), amino acids.
   • Active transport: Iron, calcium, certain vitamins (against gradient).
   • Pinocytosis: Large proteins (e.g., IgG antibodies).
4. Fetal circulation: Umbilical vein carries oxygenated/nutrient‑rich blood to fetus; two umbilical arteries return deoxygenated, waste‑laden blood to placenta.
5. No blood mixing: Maternal and fetal circulations remain separate throughout.

Clinical Relevance

Placental insufficiency (from hypertension, diabetes, smoking) impairs transport, leading to intrauterine growth restriction (IUGR). Optimal maternal nutrition and prenatal care support placental function.