Sections View Full Chapter Figures Tables Videos Full Chapter Figures Tables Videos Supplementary Content ++Table Graphic Jump LocationFavorite Table | Download (.pdf) | PrintOverview of Physiological Changes during PregnancyMean body weightIncreases by 17% on averageParenchymal organ hypertrophyIncrease in muscle massFetoplacental unitOxygen demand and CO2 productionIncreased by 30–40% at termTotal body fluids and electrolytes7 L water and 900 mEq sodium is gained by term ++Table Graphic Jump LocationFavorite Table | Download (.pdf) | PrintCardiovascular SystemCardiac outputBy 5th weekIncrease noticeableDue to increase in heart rateBy 12th week35–40% over nonpregnant valueStroke volume also increasesEnd of second trimester50% over nonpregnant valueAt term both heart rate and stroke volume increased by 25% compared with nonpregnant valuesVentricular volumesLVED increasesLVES unchangedContractilityUnchanged throughout pregnancyFilling pressuresCVP, PADP, PCWPAll unchanged compared with nonpregnant valuesSystemic vascular resistanceReduced by 20% at term compared with nonpregnant valuesSystolic blood pressureMinimally affectedDeclines by 8% at midgestationReturns to baseline at termDiastolic blood pressureReduced by 20% at midgestationReturns close to baseline at termDue to aortocaval compressionEKG changesSinus tachycardiaShortened PRQRS axis shifts initially to the right, and then to the leftST depression, T-wave changes in lead IIINew Q wave in leads III, aVFDo not confuse with myocardial ischemia, pulmonary embolismEchocardiographyBy 12th weekNoticeable LVHBy term50% increase in LV massValve annular diameters increase (except aortic valve)94% patients have tricuspid regurgitation27% have mitral regurgitationAortic insufficiency is never normal ++ The degree of compression of the aorta and inferior vena cava by the gravid uterus depends on: ++ The gestational ageThe position of the pregnant woman ++Table Graphic Jump LocationFavorite Table | Download (.pdf) | PrintEffect of Gestational Age and Position on Aortocaval Compression13–16 weeksFirst sign of IVC compression detectableAt termLateral decubitusPartial obstruction of IVCNo significant obstruction of aortaSupineFull or close to full obstruction of IVCRV filling pressure dropsCardiac output reduced by 20% or moreNoticeable compression of the abdominal aorta20% decrease in uterine blood flow50% decrease in lower extremity blood flowIncrease in SVR15° left lateral tiltReduces but does not eliminate compression of IVC and aortaSupine hypotensive syndromeBradycardiaSevere hypotensionOccurs in about 8% women at term in supine positionCombination of reduced venous return and inadequate response of the autonomic nervous system ++Table Graphic Jump LocationFavorite Table | Download (.pdf) | PrintRespiratory SystemNasopharynx and oropharynxVascular engorgementStarts as early as 7th weekBony thoraxAP and transverse diameters increaseDue to emergence of uterus from pelvisDiaphragmAt rest 4 cm higher at term compared with nonpregnant stateTidal volumeIncreased by 20% in first trimesterDue to decrease of inspiratory reserve volumeProgesterone sensitizes the respiratory center to CO2... GET ACCESS TO THIS RESOURCE Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth Get Free Access Through Your Institution Contact your institution's library to ask if they subscribe to McGraw-Hill Medical Products. What is MyAccess? Create a FREE MyAccess profile to: Use this site remotely Bookmark your favorite content Track your self-assessment progress and more! GET ACCESS TO THIS RESOURCE Subscription Options Pay Per View Timed Access to all of AccessAnesthesiology 24 Hour $34.95 (USD) Buy Now 48 Hour $54.95 (USD) Buy Now Best Value AccessAnesthesiology Full Site: One-Year Individual Subscription $995 USD Buy Now View All Subscription Options