Maternal Physiological Changes During Pregnancy, Labor, and the Postpartum Period

  • Sanjay Datta
  • Bhavani Shankar Kodali
  • Scott Segal


Maternal blood volume increases during pregnancy, and this involves an increase in plasma volume as well as in red cell and white cell volumes.1 The plasma volume increases by 40–50%, whereas the red cell volume increases by only 15–20%, which causes a “physiological anemia of pregnancy” (normal hemoglobin 12 g/dL; hematocrit 35).2 Because of this hemodilution, blood viscosity decreases by approximately 20%. The exact mechanism of this increase in plasma volume is unknown. However, several mediators such as renin–angiotensin–aldosterone, atrial natriuretic peptide, estrogen, progesterone, and nitric oxide may be involved. The most likely hypothesis attributes the increase to an “underfill” state caused by initial vasodilation, which stimulates hormones such as renin, angiotensin, and aldosterone to cause fluid retention.3 Alternatively, some have proposed an “overfill” state characterized by an early increase in sodium retention (due to an increase in mineralcorticoids) that leads to fluid retention, causing an increase in blood volume, followed subsequently by vasodilation.


Atrial Natriuretic Peptide Gravid Uterus Plasma Volume Increase Cardiac Output Increase Epidural Venous Plexus 


  1. 1.
    Lund CJ, Donovan JC. Blood volume during pregnancy. Significance of plasma and red cell volumes. Am J Obstet Gynecol. 1967;98(3):394–403.PubMedGoogle Scholar
  2. 2.
    Ueland K. Maternal cardiovascular dynamics. VII. Intrapartum blood volume changes. Am J Obstet Gynecol. 1976;126(6):671–677.PubMedGoogle Scholar
  3. 3.
    Barron WM, Mujais SK, Zinaman M, Bravo EL, Lindheimer MD. Plasma catecholamine responses to physiologic stimuli in normal human pregnancy. Am J Obstet Gynecol. 1986;154(1):80–84.PubMedGoogle Scholar
  4. 4.
    Frolich MA, Datta S, Corn SB. Thrombopoietin in normal pregnancy and preeclampsia. Am J Obstet Gynecol. 1998;179(1):100–104.CrossRefPubMedGoogle Scholar
  5. 5.
    Burrows RF, Kelton JG. Thrombocytopenia at delivery: a prospective survey of 6715 deliveries. Am J Obstet Gynecol. 1990;162(3):731–734.PubMedGoogle Scholar
  6. 6.
    Sharma SK, Philip J, Wiley J. Thromboelastographic changes in healthy parturients and postpartum women. Anesth Analg. 1997;85(1):94–98.CrossRefPubMedGoogle Scholar
  7. 7.
    Mashini IS, Albazzaz SJ, Fadel HE, et al. Serial noninvasive evaluation of cardiovascular hemodynamics during pregnancy. Am J Obstet Gynecol. 1987;156(5):1208–1213.PubMedGoogle Scholar
  8. 8.
    Chang AB. Physiologic changes of pregnancy. In: Chestnut DH, ed. Obstetric Anesthesia: Principles and Practice. Philadelphia: Elsevier-Mosby; 2004:15–36.Google Scholar
  9. 9.
    Clark SL, Cotton DB, Lee W, et al. Central hemodynamic assessment of normal term pregnancy. Am J Obstet Gynecol. 1989;161(6 Pt 1):1439–1442.PubMedGoogle Scholar
  10. 10.
    Robson SC, Hunter S, Moore M, Dunlop W. Haemodynamic changes during the puerperium: a Doppler and M-mode echocardiographic study. Br J Obstet Gynaecol. 1987;94(11):1028–1039.PubMedGoogle Scholar
  11. 11.
    Prowse CM, Gaensler EA. Respiratory and acid-base changes during pregnancy. Anesthesiology. 1965;26:381–392.CrossRefPubMedGoogle Scholar
  12. 12.
    Bayliss DA, Millhorn DE. Central neural mechanisms of progesterone action: application to the respiratory system. J Appl Physiol. 1992;73(2):393–404.PubMedGoogle Scholar
  13. 13.
    Kodali BS, Chandrasekhar S, Bulich LN, Topulos GP, Datta S. Airway changes during labor and delivery. Anesthesiology. 2008;108(3):357–362.CrossRefPubMedGoogle Scholar
  14. 14.
    Pearson JF, Davies P. The effect of continuous lumbar epidural analgesia on the acid-base status of maternal arterial blood during the first stage of labour. J Obstet Gynaecol Br Commonw. 1973;80(3):218–224.PubMedGoogle Scholar
  15. 15.
    Pearson JF, Davies P. The effect on continuous lumbar epidural analgesia on maternal acid–base balance and arterial lactate concentration during the second stage of labour. J Obstet Gynaecol Br Commonw. 1973;80(3):225–229.PubMedGoogle Scholar
  16. 16.
    Roberts RB, Shirley MA. Reducing the risk of acid aspiration during cesarean section. Anesth Analg. 1974;53(6):859–868.CrossRefPubMedGoogle Scholar
  17. 17.
    Carp H, Jayaram A, Stoll M. Ultrasound examination of the stomach contents of parturients. Anesth Analg. 1992;74(5):683–687.CrossRefPubMedGoogle Scholar
  18. 18.
    Cohen SE. Why is the pregnant patient different? Semin Anesthesia. 1982;1:73.Google Scholar
  19. 19.
    Jeyabalan A, Conrad KP. Renal function during normal pregnancy and preeclampsia. Front Biosci. 2007;12:2425–2437.CrossRefPubMedGoogle Scholar
  20. 20.
    Palahniuk RJ, Shnider SM, Eger EI, 2nd. Pregnancy decreases the requirement for inhaled anesthetic agents. Anesthesiology. 1974;41(1):82–83.CrossRefPubMedGoogle Scholar
  21. 21.
    Steinbrook RA, Carr DB, Datta S, Naulty JS, Lee C, Fisher J. Dissociation of plasma and cerebrospinal fluid beta-endorphin-like immunoactivity levels during pregnancy and parturition. Anesth Analg. 1982;61(11):893–897.CrossRefPubMedGoogle Scholar
  22. 22.
    Datta S, Migliozzi RP, Flanagan HL, Krieger NR. Chronically administered progesterone decreases halothane requirements in rabbits. Anesth Analg. 1989;68(1):46–50.CrossRefPubMedGoogle Scholar
  23. 23.
    Bromage PR. Continuous lumbar epidural analgesia for obstetrics. Can Med Assoc J. 1961;85:1136–1140.PubMedGoogle Scholar
  24. 24.
    Fagraeus L, Urban BJ, Bromage PR. Spread of epidural analgesia in early pregnancy. Anesthesiology. 1983;58(2):184–187.CrossRefPubMedGoogle Scholar
  25. 25.
    Datta S, Lambert DH, Gregus J, Gissen AJ, Covino BG. Differential sensitivities of mammalian nerve fibers during pregnancy. Anesth Analg. 1983;62(12):1070–1072.CrossRefPubMedGoogle Scholar
  26. 26.
    Flanagan HL, Datta S, Lambert DH, Gissen AJ, Covino BG. Effect of pregnancy on bupivacaine-induced conduction blockade in the isolated rabbit vagus nerve. Anesth Analg. 1987;66(2):123–126.CrossRefPubMedGoogle Scholar
  27. 27.
    Bader AM, Datta S, Moller RA, Covino BG. Acute progesterone treatment has no effect on bupivacaine-induced conduction blockade in the isolated rabbit vagus nerve. Anesth Analg. 1990;71(5):545–548.CrossRefPubMedGoogle Scholar
  28. 28.
    Butterworth JFT, Walker FO, Lysak SZ. Pregnancy increases median nerve susceptibility to lidocaine. Anesthesiology. 1990;72(6):962–965.CrossRefPubMedGoogle Scholar
  29. 29.
    Datta S, Briwa J. Modified laryngoscope for endotracheal intubation of obese patients. Anesth Analg. 1981;60:120–121.Google Scholar

Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Sanjay Datta
    • 1
    • 2
  • Bhavani Shankar Kodali
    • 1
    • 2
  • Scott Segal
    • 1
    • 2
  1. 1.Brigham & Women’s HospitalBostonUSA
  2. 2.Harvard Medical SchoolBostonUSA

Personalised recommendations