Pregnancy Physiology Quiz

Pregnancy Trimesters

• Pregnancy is divided into three trimesters, each lasting three months.

Physiological Changes During Pregnancy

• Pregnancy impacts most organ systems in the body.
• Changes are primarily adaptive and beneficial for the mother in managing the stresses of pregnancy, labor, and delivery.

Central Nervous System

• The minimum alveolar concentration (MAC) for anesthetics decreases during pregnancy, reaching up to a 40% reduction at term.
• Pregnant patients show heightened sensitivity to local anesthetics during regional anesthesia and analgesia.

Respiratory System

• Oxygen consumption and minute ventilation increase throughout pregnancy.
• Tidal volume, respiratory rate, and inspiratory reserve volume also increase.
• Partial pressure of carbon dioxide (PaCO2) decreases to 28-32 mmHg.
• Thoracic breathing becomes more prevalent than abdominal breathing.
• Functional residual capacity (FRC) decreases up to 20% at term.
• The combination of decreased FRC and increased oxygen consumption leads to rapid oxygen desaturation during periods of apnea.
• Significant respiratory alkalosis is prevented by a compensatory decrease in plasma bicarbonate concentration.
• Hyperventilation might slightly increase partial pressure of oxygen (PaO2).
• Elevation of the diaphragm is compensated by an increase in the anteroposterior diameter of the chest.

Cardiovascular System

• Cardiac output and blood volume increase to meet the metabolic demands of both the mother and fetus.
• Plasma volume increases by 55%, exceeding the 45% increase in red cell mass, resulting in dilutional anemia and reduced blood viscosity.
• Hemoglobin concentration usually remains above 11 g/dL.
• At term, blood volume increases by 1,000 to 1,500 mL in most women, reaching a total body volume of 90 mL/kg.
• Average blood loss during vaginal delivery is 400 to 500 mL compared to 800 to 1,000 mL for a cesarean section.
• Blood volume does not return to normal until 1 to 2 weeks after delivery.
• The increase in cardiac output (40% at term) is attributed to increases in heart rate (20%) and stroke volume (30%).
• Cardiac chambers enlarge, and myocardial hypertrophy is often observed on echocardiography.
• Approximately 5% of women at term develop supine hypotension syndrome, caused by complete or near-complete compression of the inferior vena cava by the gravid uterus.

Renal & Gastrointestinal System

• Renal plasma flow and glomerular filtration rate increase during pregnancy.
• Creatinine and blood urea nitrogen levels may decrease.
• Plasma osmolality decreases by 8 to 10 mOsm/kg.
• Gastroesophageal reflux and esophagitis are common during pregnancy.
• Opioid and anticholinergic drugs reduce lower esophageal sphincter pressure, potentially facilitating gastroesophageal reflux and delaying gastric emptying.

Hepatic System

• Overall hepatic function and blood flow remain unchanged.
• There is a 20 to 30% decrease in serum pseudocholinesterase activity at term.

Hematological System

• Pregnancy is associated with a hypercoagulable state.
• Fibrinogen and concentrations of factors VII, VIII, IX, X, and XII all increase.

Pregnancy

• State of carrying and developing a fetus within the female body
• Divided into three trimesters
  • First trimester: first three months
  • Second trimester: second three months
  • Third trimester: last three months
• Impacts most organ systems, many changes are adaptive and beneficial for the mother

CNS

• Minimum alveolar concentration (MAC) decreases during pregnancy
  • Decreases by as much as 40% at term
• Pregnant patients experience enhanced sensitivity to local anesthesia during regional anesthesia and analgesia

Respiratory System

• Oxygen consumption and minute ventilation increase during pregnancy
• Tidal volume, respiratory rate, and inspiratory reserve volume also increase
• PaCO2 decreases to 28 - 32 mmHg
• Thoracic breathing is favored over abdominal breathing
• Functional residual capacity (FRC) decreases up to 20% at term
  • The combination of decreased FRC and increased O2 consumption leads to rapid oxygen desaturation during periods of apnea
• Significant respiratory alkalosis is prevented by a compensatory decrease in plasma bicarbonate concentration
• Hyperventilation may slightly increase PaO2
• Elevation of the diaphragm is compensated by an increase in the anteroposterior diameter of the chest

Cardiovascular System

• Cardiac output and blood volume increase to meet maternal and fetal metabolic demands
• An increase in plasma volume (55%) exceeds the increase in red cell mass (45%)
  • Produces dilutional anemia and reduced blood viscosity
• Hemoglobin concentration typically remains greater than 11 g/dL
• At term:
  • Blood volume increases by 1,000 - 1,500 mL in most women
  • Total body volume reaches 90 mL/kg
• Average blood loss during vaginal delivery is 400 - 500 mL compared to 800 - 1,000 mL for a cesarean section
• Blood volume does not return to normal until 1 - 2 weeks after delivery
• The increase in cardiac output (40% at term) is due to increases in heart rate (20%) and stroke volume (30%)
• Cardiac chambers enlarge and myocardial hypertrophy is often observed on echocardiography
• Approximately 5% of women at term develop the supine hypotension syndrome
  • The cause of this syndrome appears to be complete or near-complete occlusion of the inferior vena cava by the gravid uterus

Renal & Gastrointestinal System

• Renal plasma flow and glomerular filtration rate increase during pregnancy
• Creatinine and blood urea nitrogen may decrease
• Plasma osmolality decreases by 8 - 10 mOsm/kg
• Gastroesophageal reflux and esophagitis are common during pregnancy
• Opioid and anticholinergic drugs reduce lower esophageal sphincter pressure, may facilitate gastroesophageal reflux and delay gastric emptying

Hepatic System

• Overall hepatic function and blood flow remain unchanged
• A 20 - 30% decrease in serum pseudocholinesterase activity at term

Hematological System

• Pregnancy is associated with a hypercoagulable state
• Fibrinogen and concentrations of factors VII, VIII, IX, X, and XII all increase

Pregnancy

• The state of carrying and developing a fetus within the female body.
• Divided into three trimesters:
  • First trimester: The first three months of pregnancy.
  • Second trimester: The second three months of pregnancy.
  • Third trimester: The last three months of pregnancy.
• Affects most organ systems.
• Many physiological changes are adaptive and helpful for the mother to tolerate the stresses of pregnancy, labor, and delivery.

CNS

• Minimum alveolar concentration (MAC) decreases during pregnancy, by as much as 40% at term.
• Pregnant patients have enhanced sensitivity to local anesthesia during regional anesthesia and analgesia.

Respiratory System

• Oxygen consumption and minute ventilation increase during pregnancy.
• Tidal volume, respiratory rate, and inspiratory reserve volume also increase.
• PaCO2 decreases to 28 – 32 mmHg.
• Thoracic breathing is favored over abdominal breathing.
• Functional residual capacity (FRC) decreases up to 20% at term.
• The combination of decreased FRC and increased oxygen consumption promotes rapid oxygen desaturation during periods of apnea.
• Significant respiratory alkalosis is prevented by a compensatory decrease in plasma bicarbonate concentration.
• Hyperventilation may slightly increase PaO2.
• Elevation of the diaphragm is compensated by an increase in the anteroposterior diameter of the chest.

Cardiovascular System

• Cardiac output and blood volume increase to meet maternal and fetal metabolic demands.
• An increase (55%) in plasma volume in excess of increased red cell mass (45%) produces dilutional anemia and reduces blood viscosity.
• Hemoglobin concentration usually remains greater than 11 g/dL.
• At term:
  • Blood volume has increased by 1000 – 1500 mL in most women.
  • Total body volume reaches 90 mL/kg.
• Average blood loss during vaginal delivery is 400 – 500 mL, compared with 800 – 1000 mL for a Cesarean section.
• Blood volume does not usually return to normal until 1 – 2 weeks after delivery.
• The increase in cardiac output (40% at term) is due to increases in heart rate (20%) and stroke volume (30%).
• Cardiac chambers enlarge, and myocardial hypertrophy is often noted on echocardiography.
• Approximately 5% of women at term develop the supine hypotension syndrome.
• The cause of this syndrome appears to be complete or near-complete occlusion of the inferior vena cava by the gravid uterus.

Renal & Gastrointestinal System

• Renal plasma flow and glomerular filtration rate increase during pregnancy.
• Creatinine and blood urea nitrogen may decrease.
• Plasma osmolality decreases by 8 – 10 mOsm/kg.
• Gastroesophageal reflux and esophagitis are common during pregnancy.
• Opioid and anticholinergic drugs reduce lower esophageal sphincter pressure, which may facilitate gastroesophageal reflux and delay gastric emptying.

Hepatic System

• Overall hepatic function and blood flow are unchanged.
• A 20 – 30% decrease in serum pseudocholinesterase activity at term.

Hematological System

• Pregnancy is associated with a hypercoagulable state.
• Fibrinogen and concentrations of factors VII, VIII, IX, X, and XII all increase.

Pregnancy

• The state of carrying a developing fetus within the female body
• Divided into three trimesters: first, second, and third trimester
• The duration of each trimester is three months
• Pregnancy greatly affects most organ systems, with many changes appearing to be adaptive to pregnancy, labor, and delivery

Central Nervous System (CNS)

• The minimum alveolar concentration (MAC) decreases during pregnancy by as much as 40% at term
• Pregnant patients are more sensitive to local anesthesia during regional anesthesia and analgesia

Respiratory System

• Oxygen consumption and minute ventilation increase during pregnancy
• Tidal volume, respiratory rate, and inspiratory reserve volume also increase
• PaCO2 decreases to 28 – 32 mmHg
• Thoracic breathing is favored over abdominal breathing during pregnancy
• Functional residual capacity (FRC) decreases up to 20% at term
• Increased oxygen consumption combined with decrease in FRC promotes rapid oxygen desaturation during apnea
• Significant respiratory alkalosis is prevented by a compensatory decrease in plasma bicarbonate concentration
• Hyperventilation may increase PaO2 slightly
• Elevation of the diaphragm is compensated by an increase in the anteroposterior diameter of the chest

Cardiovascular System

• Cardiac output and blood volume increase to meet maternal and fetal metabolism demands
• Plasma volume increases by 55% while the increase in red cell mass is 45%. This results in dilutional anemia and reduced blood viscosity
• Despite the reduced blood viscosity, Hb concentration usually remains greater than 11g/dL
• At term:
  • Blood volume increases by 1000 - 1500 mL in most women
  • Total body volume reaches 90 ml/kg
  • Average blood loss during vaginal delivery is 400 - 500 mL while Cesarean section is 800-1000 mL
  • Blood volume does not return to normal until 1-2 weeks after delivery
• The increase in cardiac output (40% at term) is due to increases in heart rate (20%) and stroke volume (30%)
• Cardiac chambers enlarge and myocardial hypertrophy are often noted on echocardiogram
• Approximately 5% of women at term develop the supine hypotension syndrome caused by complete or near-complete compression of the inferior vena cava by the gravid uterus

Renal & Gastrointestinal System

• Renal plasma flow and glomerular filtration rate increase during pregnancy
• Creatinine and blood urea nitrogen may decrease
• Plasma osmolality decreases by 8-10 mOsm/kg
• Gastroesophageal reflux and esophagitis are common during pregnancy
• Opioid and anticholinergic drugs reduce lower esophageal sphincter pressure which may facilitate gastroesophageal reflux and delay gastric emptying

Hepatic System

• Overall hepatic function and blood flow are unchanged
• A 20-30% decrease in serum pseudocholinesterase activity at term

Hematological System

• Pregnancy is associated with a hypercoagulable state
• Fibrinogen and concentrations of factors VII, VIII, IX, X, XII all increase

Pregnancy

• Pregnancy is the state of carrying and developing a fetus within the female body.
• Pregnancy is divided into three trimesters:
  • First Trimester: The first three months.
  • Second Trimester: The second three months of pregnancy.
  • Third Trimester: The last three months.
• Pregnancy affects most organ systems.

CNS

• The Minimum Alveolar Concentration (MAC) decreases during pregnancy, by as much as 40% at term.
• Pregnant patients have enhanced sensitivity to local anesthesia during regional anesthesia and analgesia.

Respiratory System

• Oxygen consumption and minute ventilation increase during pregnancy.
• Tidal volume, respiratory rate, and inspiratory reserve volume also increase.
• PaCO2 decreases to 28-32 mmHg.
• Thoracic breathing is favored over abdominal breathing.
• Functional Residual Capacity (FRC) decreases up to 20% at term.
• The combination of decreased FRC and increased O2 consumption promotes rapid oxygen desaturation during periods of apnea.
• Significant respiratory alkalosis is prevented by a compensatory decrease in plasma bicarbonate concentration.
• Hyperventilation may slightly increase PaO2.
• Elevation of the diaphragm is compensated by an increase in the anteroposterior diameter of the chest.

Cardiovascular System

• Cardiac output and blood volume increase to meet maternal and fetal metabolic demand.
• There is an increase (55%) in plasma volume in excess of increased red cell mass (45%), producing dilutional anemia and reducing blood viscosity.
• Hemoglobin concentration usually remains greater than 11 g/dL.
• At term:
  • Blood volume has increased by 1000–1500 mL in most women.
  • Total body volume reaches 90 ml/kg.
• Average blood loss during vaginal delivery is 400–500 mL compared to 800–1000 mL for a Cesarean section.
• Blood volume does not return to normal until 1–2 weeks after delivery.
• The increase in cardiac output (40% at term) is due to increases in heart rate (20%) and stroke volume (30%).
• Cardiac chambers enlarge, and myocardial hypertrophy is often noted in echocardiography.
• Approximately 5% of women at term develop the supine hypotension syndrome.
• The cause of the syndrome appears to be the complete or near-complete occlusion of the inferior vena cava by the gravid uterus.

Renal & Gastrointestinal System

• Renal plasma flow and glomerular filtration rate increase during pregnancy.
• Creatinine and blood urea nitrogen may decrease.
• Plasma osmolality decreases by 8–10 mOsm/kg.
• Gastroesophageal reflux and esophagitis are common during pregnancy.
• Opioid and anticholinergic drugs reduce lower esophageal sphincter pressure, which may facilitate gastroesophageal reflux and delay gastric emptying.

Hepatic System

• Overall hepatic function and blood flow are unchanged.
• There is a 20–30% decrease in serum pseudocholinesterase activity at term.

Hematological System

• Pregnancy is associated with a hypercoagulable state.
• Fibrinogen and concentrations of factors VII, VIII, IX, X, and XII all increase.

Pregnancy

• Carrying and developing a fetus within the female body
• Divided into three trimesters: first, second, and third trimesters, each lasting three months
• Affects most organ systems with changes being adaptive to tolerate the stresses of pregnancy, labor, and delivery

CNS

• Decreased Minimum Alveolar Concentration (MAC) during pregnancy, up to 40% at term
• Increased sensitivity to Local Anesthesia during regional anesthesia and analgesia

Respiratory System

• Increased oxygen consumption and minute ventilation
• Increased tidal volume, respiratory rate, and inspiratory reserve volume
• Decreased PaCo2 to 28-32 mmHg
• Thoracic breathing favored over abdominal breathing
• Decreased Functional Residual Capacity (FRC) by up to 20% at term contributing to rapid oxygen desaturation during apnea
• Significant respiratory alkalosis is prevented by decreased plasma bicarbonate concentration
• Hyperventilation slightly increases Pao2
• Diaphragm elevation is compensated by increased anteroposterior diameter of the chest

Cardiovascular System

• Increased cardiac output and blood volume to meet maternal and fetal metabolic demand
• Plasma volume increases by 55% exceeding the 45% increase in red cell mass, causing dilutional anemia and reduced blood viscosity
• Hemoglobin concentration remains greater than 11 g/dL
• At term, blood volume increases by 1000-1500 mL and total body volume reaches 90 mL/kg
• Average blood loss during vaginal delivery is 400-500 mL, compared to 800-1000 mL for a cesarean section
• Blood volume doesn’t return to normal until 1-2 weeks after delivery
• Increased Cardiac Output (40% at term) due to increased heart rate (20%) and stroke volume (30%)
• Cardiac chambers enlarge and myocardial hypertrophy is often noted during echocardiography
• Approximately 5% of women at term develop supine hypotension syndrome caused by compression of the inferior vena cava by the gravid uterus

Renal & Gastrointestinal System

• Increased renal plasma flow and glomerular filtration rate
• Decreased Creatinine and blood urea nitrogen
• Decreased Plasma Osmolality by 8-10 mOsm/kg
• Gastroesophageal reflex and esophagitis are common
• Opioid and anticholinergic drugs reduce lower esophageal sphincter pressure, facilitating gastroesophageal reflex and delaying gastric emptying

Hepatic System

• Overall hepatic function and blood flow remain unchanged
• 20-30% decrease in serum pseudocholinesterase activity at term

Hematological System

• Pregnancy associated with hypercoagulable state
• Increased Fibrinogen and concentrations of factors VII, VIII, IX, X, XII

Pregnancy & Trimesters

• Pregnancy involves the development of a fetus within the female body.
• It's divided into three trimesters, each lasting three months.

Central Nervous System (CNS)

• Minimum alveolar concentration (MAC) decreases during pregnancy, reaching up to a 40% reduction by term.
• Pregnant patients exhibit enhanced sensitivity to local anesthesia during regional anesthesia and analgesia.

Respiratory System

• Oxygen consumption and minute ventilation increase during pregnancy.
• Tidal volume, respiratory rate, and inspiratory reserve volume also increase.
• PaCO2 decreases to 28-32 mmHg.
• Thoracic breathing is favored over abdominal breathing.
• Functional residual capacity (FRC) decreases up to 20% at term.
• The combined effect of decreased FRC and increased oxygen consumption promotes rapid oxygen desaturation during periods of apnea.
• Significant respiratory alkalosis is prevented by a compensatory decrease in plasma bicarbonate concentration.
• Hyperventilation may slightly increase PaO2.
• Elevation of the diaphragm is compensated by an increase in the anteroposterior diameter of the chest.

Cardiovascular System

• Cardiac output and blood volume increase to meet maternal and fetal metabolic demands.
• Plasma volume increases by 55%, exceeding the 45% increase in red cell mass, resulting in dilutional anemia and reduced blood viscosity.
• Hemoglobin concentration typically remains above 11 g/dL.
• At term, blood volume has increased by 1000-1500 mL in most women.
• Total body volume reaches 90 mL/kg.
• Average blood loss during vaginal delivery is 400-500 mL, compared to 800-1000 mL for a Cesarean section.
• Blood volume does not return to normal until 1-2 weeks after delivery.
• The increase in cardiac output (40% at term) is attributed to increases in heart rate (20%) and stroke volume (30%).
• Cardiac chambers enlarge and myocardial hypertrophy is often observed on echocardiography.
• Approximately 5% of women at term develop supine hypotension syndrome, potentially caused by compression of the inferior vena cava by the gravid uterus.

Renal & Gastrointestinal System

• Renal plasma flow and glomerular filtration rate increase during pregnancy.
• Creatinine and blood urea nitrogen levels may decrease.
• Plasma osmolality decreases by 8-10 mOsm/kg
• Gastroesophageal reflux and esophagitis are common during pregnancy.
• Opioid and anticholinergic drugs reduce lower esophageal sphincter pressure, potentially contributing to gastroesophageal reflux and delayed gastric emptying.

Hepatic System

• Overall hepatic function and blood flow remain unchanged.
• A 20-30% decrease in serum pseudocholinesterase activity occurs at term.

Hematological System

• Pregnancy is associated with a hypercoagulable state.
• Fibrinogen and concentrations of factors VII, VIII, IX, X, and XII all increase.

Pregnancy Physiology Changes

• Pregnancy is the state of carrying and developing a fetus within the female body.
• Three trimesters:
  • First trimester: First three months
  • Second trimester: Second three months
  • Third trimester: Last three months
• Pregnancy affects most organ systems, with many changes being adaptive and beneficial for the mother.

Central Nervous System (CNS)

• Minimum alveolar concentration (MAC): Decreases during pregnancy, up to 40% at term.
• Sensitivity to local anesthesia: Increased sensitivity during regional anesthesia and analgesia.

Respiratory System

• Oxygen consumption & minute ventilation: Increase during pregnancy.
• Tidal volume, respiratory rate, and inspiratory reserve volume: Also increase.
• PaCO2: Decreases to 28 – 32 mmHg.
• Thoracic breathing: Favored over abdominal breathing.
• Functional residual capacity (FRC): Decreases up to 20% at term. This, combined with increased oxygen consumption, leads to rapid oxygen desaturation during apnea.
• Respiratory alkalosis: Prevented by a compensatory decrease in plasma bicarbonate concentration.
• Hyperventilation: May slightly increase PaO2.
• Diaphragm elevation: Compensated by an increase in the anteroposterior diameter of the chest.

Cardiovascular System

• Cardiac output and blood volume: Increase to meet maternal and fetal metabolic demand.
• Plasma volume: Increases by 55%, exceeding the increase in red cell mass (45%), resulting in dilutional anemia and reduced blood viscosity.
• Hemoglobin concentration: Usually remains above 11 g/dL.
• Blood volume at term: Increases by 1000-1500 mL in most women, reaching 90 mL/kg.
• Blood loss during delivery: 400-500 mL for vaginal delivery and 800-1000 mL for cesarean section.
• Blood volume return to normal: Occurs 1-2 weeks after delivery.
• Cardiac output increase: At term, increases by 40%, due to increases in heart rate (20%) and stroke volume (30%).
• Cardiac chamber enlargement & myocardial hypertrophy: Often observed on echocardiography.
• Supine hypotension syndrome: Affects approximately 5% of women at term. This syndrome is caused by compression of the inferior vena cava by the gravid uterus.

Renal & Gastrointestinal System

• Renal plasma flow and glomerular filtration rate: Increase during pregnancy.
• Creatinine and blood urea nitrogen: May decrease.
• Plasma osmolality: Decreases by 8-10 mOsm/kg.
• Gastroesophageal reflux and esophagitis: Common during pregnancy.
• Opioids and anticholinergic drugs: Reduce lower esophageal sphincter pressure, facilitating gastroesophageal reflux and delaying gastric emptying.

Hepatic System

• Overall hepatic function and blood flow: Remain unchanged.
• Serum pseudocholinesterase activity: Decreases by 20-30% at term.

Hematological System

• Hypercoagulable state: Associated with pregnancy.
• Fibrinogen and concentrations of factors VII, VIII, IX, X, XII: All increase.

Pregnancy

• Pregnancy is the state of carrying and developing a fetus within the female body.
• Pregnancy is divided into three trimesters: first, second, and third.
• The first trimester is the first three months of pregnancy.
• The second trimester is the second three months of pregnancy.
• The third trimester is the last three months of pregnancy.

Central Nervous System (CNS)

• Minimum alveolar concentration (MAC) decreases during pregnancy, by as much as 40% at term.
• Pregnant patients have enhanced sensitivity to local anesthesia during regional anesthesia and analgesia.

Respiratory System

• Oxygen consumption and minute ventilation increase during pregnancy.
• Tidal volume, respiratory rate, and inspiratory reserve volume increase.
• PaCO2 decreases to 28-32 mmHg.
• Thoracic breathing is favored over abdominal breathing.
• Functional residual capacity (FRC) decreases up to 20% at term.
• The combination of decreased FRC and increased O2 consumption promotes rapid oxygen desaturation during periods of apnea.
• Significant respiratory alkalosis is prevented by a compensatory decrease in plasma bicarbonate concentration.
• Hyperventilation may slightly increase PaO2.
• Elevation of the diaphragm is compensated by an increase in the anteroposterior diameter of the chest.

Cardiovascular System

• Cardiac output and blood volume increase to meet maternal and fetal metabolic demands.
• An increase (55%) in plasma volume in excess of red cell mass increase (45%) produces dilutional anemia and reduces blood viscosity.
• Hemoglobin concentration usually remains greater than 11g/dL.
• At term, blood volume increases by 1000-1500 mL in most women.
• Total body volume reaches 90 ml/kg.
• Average blood loss during vaginal delivery is 400-500 mL, compared with 800-1000 mL for a cesarean section.
• Blood volume does not return to normal until 1-2 weeks after delivery.
• The increase in cardiac output (40% at term) is due to increases in heart rate (20%) and stroke volume (30%).
• Cardiac chambers enlarge and myocardial hypertrophy is often noted on echocardiography.
• Approximately 5% of women at term develop the supine hypotension syndrome.
• The cause of this syndrome appears to be complete or near-complete occlusion of the inferior vena cava by the gravid uterus.

Renal and Gastrointestinal System

• Renal plasma flow and glomerular filtration rate increase during pregnancy.
• Creatinine and blood urea nitrogen may decrease.
• Plasma osmolality decreases by 8-10 mOsm/kg.
• Gastroesophageal reflux and esophagitis are common during pregnancy.
• Opioid and anticholinergic drugs reduce lower esophageal sphincter pressure, which may facilitate gastroesophageal reflux and delay gastric emptying.

Hepatic System

• Overall hepatic function and blood flow remain unchanged.
• There is a 20-30% decrease in serum pseudocholinesterase activity at term.

Hematological System

• Pregnancy is associated with a hypercoagulable state.
• Fibrinogen and concentrations of factors VII, VIII, IX, X, and XII all increase.

Pregnancy and the CNS

• Minimum alveolar concentration (MAC) decreases during pregnancy, by as much as 40% at term
• Pregnant patients have a higher sensitivity to local anesthetics during regional anesthesia and analgesia

Pregnancy and the Respiratory System

• Oxygen consumption and minute ventilation increase during pregnancy
• Tidal volume, respiratory rate, and inspiratory reserve volume increase
• PaCO2 decreases to 28-32 mmHg
• Thoracic breathing is favored over abdominal breathing
• Functional residual capacity (FRC) decreases up to 20% at term
• Decreased FRC and increased oxygen consumption lead to rapid oxygen desaturation during apnea
• Significant respiratory alkalosis is prevented by a decrease in plasma bicarbonate concentration
• Hyperventilation slightly increases PaO2
• The diaphragm is elevated and compensated by an increase in the anteroposterior diameter of the chest

Pregnancy and the Cardiovascular System

• Cardiac output and blood volume increase to meet maternal and fetal metabolic demand
• Plasma volume increases by 55% while red cell mass increases by 45%, producing dilutional anemia and reducing blood viscosity
• Hemoglobin concentration usually remains greater than 11 g/dL
• At term, blood volume has increased by 1000-1500 mL in most women
• Total body volume reaches 90 ml/kg
• Average blood loss during vaginal delivery is 400-500 mL, compared to 800-1000 mL for a cesarean section
• Blood volume does not return to normal until 1-2 weeks after delivery
• Cardiac output increases by 40% at term due to increased heart rate (20%) and stroke volume (30%)
• Cardiac chambers enlarge, and myocardial hypertrophy is often noted on echocardiography
• Approximately 5% of women at term develop the supine hypotension syndrome
• The cause of this syndrome is compression of the inferior vena cava by the gravid uterus

Pregnancy and the Renal and Gastrointestinal System

• Renal plasma flow and glomerular filtration rate increase during pregnancy
• Creatinine and blood urea nitrogen may decrease
• Plasma osmolality decreases by 8-10 mOsm/kg
• Gastroesophageal reflux and esophagitis are common during pregnancy
• Opioid and anticholinergic drugs reduce lower esophageal sphincter pressure, facilitating gastroesophageal reflux and delaying gastric emptying

Pregnancy and the Hepatic System

• Overall hepatic function and blood flow are unchanged
• A 20-30% decrease in serum pseudocholinesterase activity at term

Pregnancy and the Hematologic System

• Pregnancy is associated with a hypercoagulable state
• Fibrinogen and concentrations of factors VII, VIII, IX, X, XII increase