Placental O2 Exchange

  • Cassandra Wasson
  • Albert Kelly
  • David Ninan
  • Quy Tran


This chapter discusses oxygen transfer of the placental. It discusses fetal oxygen uptake, oxygen affinity, and the role of the Bohr effect.


Oxygen transfer Fetal oxygen uptake Oxygen affinity Oxygen-carrying capacity Bohr effect 
  1. 1.

    The placenta is the fetal “lung” and has a fifth of the O2 transfer efficiency of the adult lung

  2. 2.

    Placenta provides ~8 mL O2/min/kg fetal body weight

  3. 3.

    Delivery of oxygen to the fetus is predominantly flow limited (i.e., maternal delivery of blood to the uterus controls fetal oxygen transfer)

  4. 4.
    O2 transfer across the placenta depends on the O2 partial pressure gradient between maternal blood and fetal blood
    1. (a)

      O2 dissolved in plasma diffuses across the villous membranes and O2 bound to hemoglobin (Hgb) is released and diffuses across the placenta

  5. 5.
    Factors favoring fetal oxygen uptake:
    1. (a)

      Oxygen affinity: Fetal oxyhemoglobin (Hb F) dissociation curve is shifted left (high oxygen affinity; P50: 19 mmHg) and maternal (Hb A) dissociation curve is shifted right (P50: 27 mmHg), allowing greater O2 transfer to fetus

    2. (b)

      Oxygen-carrying capacity: The hemoglobin concentration of fetal blood is high 15 g/dL compared with the mother’s 12 g/dL

  6. 6.

    Bohr effect also enhances O2 transfer to fetus; fetal-maternal transfer of CO2 makes maternal blood more acidotic and fetal blood more alkalotic causing a shift in maternal and fetal oxyhemoglobin dissociation curves favoring unloading of maternal oxygen to fetus


Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Cassandra Wasson
    • 1
  • Albert Kelly
    • 1
  • David Ninan
    • 2
  • Quy Tran
    • 3
  1. 1.Riverside University Health System - Medical CenterMoreno ValleyUSA
  2. 2.Riverside University Health System - Medical CenterLoma LindaUSA
  3. 3.Harbor–UCLA Medical CenterTorranceUSA

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