Maternal Physiology in Pregnancy
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Maternal Physiology in Pregnancy

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Detailed account of the various changes that occur in maternal anatomy, physiology, and metabolism of pregnant women. These physiological changes are often very precise, and deviations of ...

Detailed account of the various changes that occur in maternal anatomy, physiology, and metabolism of pregnant women. These physiological changes are often very precise, and deviations of physiological responses can be a prelude to possible disease/infectious states. In this second part of Labor, we will examine the various systems of the human body,its altered states during pregnancy, and how those changes affect the woman preparing for delivery. Special care is imperative in properly determining the needs of an expecting mother, so developing an intimate, trusting relationship between the mother and fully understanding her physiological output will lead to the best chances of a successful delivery.

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Maternal Physiology in Pregnancy Maternal Physiology in Pregnancy Presentation Transcript

  • Maternal Physiology in Pregnancy
    By La Lura White MD
    Maternal Fetal Medicine
  • Maternal Physiology in Pregnancy
    Major adaptations in maternal anatomy, physiology, and metabolism are required for successful pregnancy.
    Nearly every organ system is affected.
    Understanding these changes helps to distinguish the normal physiology of pregnancy from pathological disease states.
  • Maternal Physiology in Pregnancy
    These changes create a myriad of pregnancy symptoms that include
    Nausea/Emesis (morning sickness)
    Headaches
    Backaches
    Urinary frequency
    Hemorrhoids/Constipation
    Leg Cramps
    Edema more common lower extremity
    Breast tenderness
    Paresthesis
    Varicose veins
  • Maternal Physiology in Pregnancy
    Due to the pregnancy effect on major organ systems including:
    Nutritional
    Digestive Tract Changes
    Urinary System
    Cardiovascular System
    Respiratory System
    Metabolism
    Skeletal
    Endocrine
    Integument
    Ocular
  • Maternal Physiology in Pregnancy: Nutritional
    During pregnancy, nutritional requirements, including those for vitamins and minerals, are increased, and several maternal alterations occur to meet this demand.
    Addition of 300 kcal/day.
    The mother`s appetite usually increases, so that food intake is greater, although some women have a decreased appetite or experience nausea and vomiting.
    These symptoms may be related relaxation of smooth muscle, increasing levels of human chorionic gonadotrophin (hCG) and estrogen.
  • Maternal Physiology in Pregnancy
    Complicates 70% of pregnancies normally from 4-16 weeks
    True Hyperemesis gravidarum (HG) is a severe form of morning sickness, with "unrelenting, excessive pregnancy-related nausea and/or vomiting that prevents adequate intake of food and fluids, “that may requiring hospitalization, IV fluids, anti-emetics even protonics or TPN
    Pica: craving for substances that are not food
    Etiology unknown
    Check for poor weight gain and refractory anemia
    South - clay or starch (laundry or cornstarch)
    UK – coal
    Also soap, toothpaste and ice
  • Maternal Physiology in Pregnancy: Digestive Tract Changes
    If the pH of the oral cavity decreases, tooth decay may occur linked to pre-term deliveries.
    Tooth decay during pregnancy, however, is not due to lack of calcium in the teeth, dental calcium is stable and not mobilized during pregnancy as is bone calcium.
    The gums may become hypertrophic, hyperemic and friable; this maybe due to increased systemic estrogen.
    Vitamin C deficiency also can cause tenderness and bleeding of the gums.
  • Maternal Physiology in Pregnancy: Digestive Tract Changes
    Gingivitis of pregnancy: vascular swelling of the gums can lead to the development of pyogenic granulomas :
    Epulis gravidarum:
    regress 1-2 mos after delivery
    excise if persistent or excessive bleeding
  • Maternal Physiology in Pregnancy: Digestive Tract Changes
    Gastrointestinal Motility
    Reduced during pregnancy due to increased levels of progesterone, which decrease the production of motilin, a hormonal peptide that is known to stimulate smooth muscle in the gut.
    Transit time of food throughout the gastrointestinal tract much slower, more water than normal is reabsorbed, leading to constipation.
  • Maternal Physiology in Pregnancy: Digestive Tract Changes
    Decreased tone and motility secondary to progesterone
    Esophagus :dysmotility
    Esophageal peristalses is deceased, accompanied by gastric reflux because of the slower emptying time and dilatation or relaxation of the cardiac sphincter.
    Stomach
    Reduced tone of the gastroesophageal junction sphincter
    Production of the hormone gastin increases significantly, resulting in increased stomach volume and decreased stomach pH.
  • Maternal Physiology in Pregnancy
    Gastric compression due to enlarging uterus with decrease sphincter tone increasing incidence GERD
    This reflux is more prevalent in later pregnancy owing to elevation of the stomach by the enlarged uterus, making the use of anesthesia, especially general anesthesia more hazardous because of the increased possibility of regurgitation and aspiration.
    Lower incidence of PUD (peptic ulcer disease)
    may be due to decreased gastric acid secretion delayed emptying, increase in gastric mucus, and protection of mucosa by prostaglandins
  • Maternal Physiology in Pregnancy: Digestive Tract Changes
    Small bowel :
    Reduced motility and tone are allow for more efficient absorption, especially iron
    Large Bowel:
    Decreased transit times allows for both water and sodium absorption.
    Increased portal hypertension with dilation wherever there are porto-systemic venous anastamoses (varices) affecting esophagus, vulva and increase varicose veins and hemorrhoids may lead to ovarian vein thrombosis
  • Maternal Physiology in Pregnancy: Gastrointestinal Changes
    Gallbladder
    Decreased rate of emptying and hypotonia of the smooth muscle wall
    Emptying time is slowed and often incomplete
    Bile can become thick, and bile stasis
    Cholesterol saturation is increased while chenodeoxycholic acid is decreased in bile
    These changes favor the development of gallstones
  • Maternal Physiology in Pregnancy: Gastrointestinal Changes
    Liver
    Liver size and histology are unchanged
    Serum albumin and total protein decrease so there is a decrease in the albumin/globulin ratio
    Serum alkaline phosphatase increases due to placental and some hepatic production
    No change in serum bilirubin, AST, ALT
    Clinical and laboratory changes mimic disease states
    Spider angiomas and palmar erythema
  • Maternal Physiology in Pregnancy: Urinary System
    Anatomic Changes
    Renal hypertrophy
    Dilatation renal pelvis/calyces 15mm on the right in 3rd trimester 5mm on the left.
    Each kidney increases in length by 1-1.5cm, with a concomitant increase in weight.
    The ureters are dilated to 2 cm resulting in hydroureter from:
    progesterone-induced smooth muscle relaxation causing hypotonia
    mechanical compression above the brim of the bony pelvis by the ovarian vein complex in the suspensory ligament of the ovary
    dextorotation of the uterus during pregnancy, may explain why the right ureter is usually more dilated than the left.
  • Maternal Physiology in Pregnancy: Urinary System
    Hyperplasia of smooth muscle in distal one-third of the ureter may cause reduction in the luminal size
    The ureters also elongate, widen, and become more curved: there is an increase in urinary stasis
    This may lead to infection and predispose to pyelonephritis in the presence of asymptomatic bacteriuria (30%)
  • Maternal Physiology in Pregnancy: Urinary System
    Bladder
    As the uterus enlarges, the urinary bladder is displaced upward and flattened in the anterior-posterior diameter
    Bladder vascularity increases and muscle tone decreases, increasing capacity up to 1500ml.
    Trigone elevation occurs with increased vascular tortuousity throughout the bladder leading to microhematuira
    Decrease bladder capacity
    Increased frequency of urinary incontinence
  • Maternal Physiology in Pregnancy: Urinary System
    Renal Hemodynamic
    Renal blood flow increases 50% .
    GFR increases 50% (120cc/min180cc/m.)
    The renal plasma flow rate increases by as much as 25-50%..
    Serum Creatinine and BUN levels decrease.
    Urinary flow and sodium excretion rates in late pregnancy can be altered by posture, being twice as great in the lateral recumbent position as in the supine position.
    Even thought the GFR increased dramatically during pregnancy, the volume of the urine passed each day is not increased.
  • Maternal Physiology in Pregnancy: Urinary System
    With the increase in GFR, there is an increase in endogenous clearance of creatinine.
    The concentration of creatinine in serum is reduced in proportion to increase in GFR, and concentration of blood urea nitrogen is similarly reduced.
    Glucosuria during pregnancy is not necessarily abnormal, may be explained by the increase in GFR with impairment or exceeding tubular reabsortion capacity for filtered glucose.
    Increased levels of urinary glucose also contribute to increased susceptibility of pregnant women to urinary tract infection.
    Proteinuria changes little during pregnancy and if more than 300mg/24h is lost, a disease process should be suspected.
  • Maternal Physiology in Pregnancy: Urinary System
    Levels of the enzyme renin, which is produced in kidney, increase early in the first trimester, and continue to rise until term
    This enzyme acts on its substrate angiotensinogen, to first form angiotensin1 and then angiotensin2, which acts as a vasoconstrictor
    Normal pregnant women are resistant to the pressor effect of elevated levels of angiotensin2 but those suffering from preeclampsia are not resistant, this is one of the some theories to explain this disease.
  • Maternal Physiology in Pregnancy: Cardiovascular System
    As the uterus enlarges and the diaphragm becomes elevated, the heart is displaced upward and somewhat to the left with rotation on its long axis, so that the apex beat is moved laterally. (apparent cardiomegaly on chest x-ray)
    Cardiac capacity increases by 70-80mL.
    This may be due to increased volume or hypertrophy of cardiac muscle.
    The size of the heart appears to increase by about 12%.
    Increase in left ventricular end- diastolic dimension.
    Increase in left ventricular wall mass c/w mild hypertrophy.
    Increase in preload with increase capacitance of the systemic and pulmonary vascular resistances prevenst rise in CVP or wedge pressure.
    Grade II-III systolic flow murmurs at left lower sternal border.
  • Maternal Physiology in Pregnancy: Cardiovascular System
    30-35% in CO (CO= SV x HR), reaching its maximum at 20-24 weeks gestation and continuing at this level until term
    The increase in output can be as much as1.5L/min over the non pregnant level
    HR increases as early as 5 weeks GA
    Peaks at 32 weeks at 15-20 beats above baseline(20% increase)
    Stroke volume increases as early as 8 weeks GA, peaks at 20 weeks with a 20-30% increase
    Cardiac output is very sensitive to changes in body position.
  • Maternal Physiology in Pregnancy: Cardiovascular System
    This sensitivity increases with gestational age, presumably because the uterus impinges upon the inferior vena cava, thereby decreasing blood return to the heart
    Because blood pressure either decreases or remain the same during pregnancy and cardiac output increases appreciably, there is good evidence that peripheral resistance( Peripheral resistance equals blood pressure divided by cardiac output) declines markedly.
    The elevated venous pressure returns toward normal if the woman lies in the lateral recumbent position.
  • Maternal Physiology in Pregnancy Position effects on CV system
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Effects of the Labor on the Cardiovascular System
    When a patient is the supine position, uterine contractions can cause a 25% increase in maternal cardiac output, a 15% decrease in heart rate, and a resultant 33% increase in stroke volume.
    However when the laboring patient is in the recumbent position, the hemodynamic parameters stabilize , with only a 7.6% increase in cardiac output, a 7% decrease in heart rate, and a 7.7% increase in stroke volume
    These significant differences are attributable to inferior vena caval occlusion caused by the gravid uterus
  • Maternal Physiology in Pregnancy: Cardiovascular System
    During contractions, pulse pressure increases 26% in the supine position but only 6% in the lateral recumbent position.
    Important to have laboring patients in the left lateral recumbent position
  • Maternal Physiology in Pregnancy: Cardiovascular System
    BP= CO x SVR
    SVR decreases to a minimum at midpregnancy with a gradual rise towards term but still 20% lower than non-pregnancy
    Decrease SVR secondary to hormonal vasodilatation (progesterone), NO, prostaglandins, ANP
    BP changes nadir by midpregancy
    Diastolic and mean pressure decrease more than the systolic
    Increases to baseline in third trimester
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Other cardiovascular changes:
    Increases in CO, HR
    Decreases in SVR, PVR
    No change in MAP, PCWP, CVP,
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Blood Volume `
    Increase in the blood volume beginning at 6 weeks and plateaus at 30 weeks
    The magnitude of the increases varies according to the size of woman, the number of pregnancies she has had, the number of infants she has delivered, and whether there is one or multiple fetuses
    Both plasma volume (50%)and cell mass (30%) increase
    Physiologic anemia of pregnancy nadiring at 30 weeks
  • Maternal Physiology in Pregnancy: Cardiovascular System
    By term, the average increase in volume 45-50%
    The increase is needed for extra blood flow to the uterus, extra metabolic needs of fetus, and increased perfusion of others organs, especially kidneys
    Extra volume also compensate for maternal blood loss delivery
    The average blood loss with vaginal delivery is 500ml, cesarean section is 1000ml and C/Hyst 1500 ml
    10% drop HCT can be considered post-partum hemorrhage
  • Maternal Physiology in Pregnancy: Cardiovascular System
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Blood Volume
    Singleton (n=50)
    3rd trim. non-preg. % increase
    Blood volume 4820 3250 48
    RBC volume 1790 1355 32
    Hct (%) 37.0 41.7
    Pritchard, JA. Changes in blood volume during pregnancy
    5th percentile for hemoglobin was 11.0 g/L in the 1st trimester; in the 2nd trimester it was 10.5 g/L and 10.3 g/L in the third trimester
    Acta Obstet Gynecol Scand. 2000 Feb;79(2):89-98
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Iron Metabolism
    Absorption in the duodenum in the divalent state
    Trivalent food source must be converted by ferric reductase to divalent form
    Febound transferrintransported to liver, spleen, muscle and bone marrow incorporated into hemoglobin, myoglobin, ferritin or hemosiderin
    1000mg iron requirement, (about 3.5 mg/d)
    Requirements increase in third trimester
    Fetus receives Fe through active transport
  • Maternal Physiology in Pregnancy: Cardiovascular System
    With the increase in red blood cells, the need for iron for the production of hemoglobin increases, but Fe supplementation usually not needed before 20 weeks
    Fe supplementation
    Ferrous sulfate 20% ( 65mg elemental Fe) Ferrous gluconate 12% (35mg of elemental Fe) and ferrous fumarate 33%(108mg of elemental Fe) ; fumerate and gluconate better absorbed(organic Fe)
    For severe anemia:
    Preparations
    Iron Dextran (Imferon, Dexferrum)
    High rate of serious reaction (requires test dose)
    Intramuscular or Intravenous
    Dose based on estimated iron deficits
  • Maternal Physiology in Pregnancy: Cardiovascular System
    (Test dose)[25 mg] [100 ml] [5 min][Prescribed dose] [250 to 1000mg](Usually 500 ml NS)
    Total dose infusion: infuse over 2 to 6 hours.
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Sodium ferric gluconate (Ferrlecit)
    Dosing: 125 mg/weekly IV for 8 weeks (total: 1 gram)
    Much safer than Iron Dextran (no test dose needed)
    Iron sucrose (Venofer)
    Much safer than Iron Dextran (no test dose needed)
    Dosing: 200 mg IV for 5 doses over 2 week period
    Precautions
    Intravenous iron must be started very slowly
    Adverse affects: fever, pain, headaches, Myalgias and arthralgias
    Anaphylaxis
    Occurs in 0.61% of patients given Iron Dextran
    Occurs in 0.04% of patients given ferric gluconate
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Maternal requirements can reach 5-6mg/d in the latter half of pregnancy
    If supplemental iron is not added to the diet, iron deficiency anemia will result
    If iron is not readily available, the fetus, uses iron from maternal stores.
    Thus, the production of fetal hemoglobin is usually adequate even if the mother is severely iron deficient and anemia in the newborn is rarely a problem
    Maternal iron deficiency more commonly may cause preterm labor and late spontaneous abortion,
  • Maternal Physiology in Pregnancy: Cardiovascular System
    White Blood Cells
    The total blood leukocyte count increases during pregnancy from a pre-pregnancy level of 4300-4500/mL to 5000-12000/mL in the last trimester, although counts as high as 16000/mL have been observed in the last trimester
    Counts as high as 25000-30000/mL have been noted in a normal patient during labor
    Lymphocyte and monocyte numbers stay the same throughout pregnancy; polymorphonuclear leucocytes are the primary contributors to the increase.
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Platelets
    Progressive decline in count from 1st-3rd trimester.
    Increased platelet destruction.
    Plts range between 70-150,000, gestational thrombocytopenia of pregnancy Burrows @Kelton reported an 8% prevalence.
    Diagnosis of exclusion: PIH/HELLP, ITP, viral disease, HIV, autoimmune disease, ie lupus.
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Other Hematologic Changes
    Leukocytosis secondary to increase neutophils estrogen and cortisol induced
    Altered immune status, immunocompromised
    Paradoxical decline of immunoglobins A,G,M
    Only IgG crosses the placenta
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Coagulation System
    Hypercoaguable state
    Increased venous stasis lead to vessel wall injury
    Changes in the coagulation cascade
    Increases in factors I,VII,VIII, IX and X
    Unchanged or mildly increasedfactors II, V, XII
    Decrease in factors XI, XIII
    Decrease in fibrinolysis with decreased plasminogen activator
    Increase in factor I (fibrinogen) causes elevated sed rate
    Decrease in protein S but no change in protein C and antithrombin III. Activated protein C decreases
  • Maternal Physiology in Pregnancy: Cardiovascular System
    Fibrinolytic activity is depressed during pregnancy and labor, although the precise mechanism is unknown
    The placenta may be partially responsible for this alteration in fibrinolytic status
    Plasminogen levels increase concomitantly with fibrinogens levels, causing an equilibration of clotting and lysing activity
  • Maternal Physiology in Pregnancy:Respiratory System
    Anatomic and Physiologic Changes Pregnancy produces changes that affect respiratory performance
    Early in pregnancy, capillary dilatations occurs throughout the respiratory tract, leading to engorgement of the nasopharnyx, larnyx, trachea, and bronchi
    This causes the voice to change and makes breathing though the nose difficult.
    Upper respiratory tract hyperemia and edema induced by estrogen leading to nasal stuffiness and epistaxis
    Chest X-rays reveal increased vascular makings in the lungs.
  • Maternal Physiology in Pregnancy:Respiratory System
    As the uterus enlarges, the diaphragm is elevated as much as 4cm, but elevation of the diaphragm does not impede its movement.
    The rib cage is displaced upward and widens, increasing the lower thoracic diameter by 2cm and the thoracic circumference by up to 6cm.
    Chest circumference expands 5-7 cm
    Subcostal angle increases from 68 to 103 degrees
    Respiratory muscle function is not affected by pregnancy
    Abdominal muscles have less tone and are less active during the pregnancy, causing respiration to be more rather than less diaphragmatic.
  • Maternal Physiology in Pregnancy:Respiratory System
    Elevation of the diaphragm decreases the volume of the lungs in the resting state, reducing TLC by 5% and FRC by 20%
    FRC mainly decreased by RV
    Vital capacity does not change
    Chronic hyperventilation progesterone induced
    Minute volume is increased
    Tidal volume is increased
    Respiratory rate is unchanged( Increased early in the first trimester)
  • Maternal Physiology in Pregnancy:Respiratory System
    Dead volumes increase owing to relaxation of the musculature of conducting airways.
    Tidal volumes increases gradually(35-50%)as pregnancy progresses.
    Total lung capacity is reduced (4-5%) by the elevation of the diaphragm.
    Functional residual capacity, residual volume, and respiratory reserve volume all decrease by about 20%.
    Larger tidal volume and smaller residual volume cause increased alveolar ventilation (about 65%) during pregnancy.
    Inspiratory capacity increases 5-10%.
  • Maternal Physiology in Pregnancy:Respiratory System
    Functional respiratory changes include a slight increase in respiratory rate, a 50% increase in minute ventilation, a 40% increase in tidal volume
    A progressive increase in oxygen consumption of up to 15-20% above non-pregnant levels by term.
    With the increase in respiratory tidal volume associated with a normal respiratory rate, there is an increase in respiratory minute volume of approximately 26%
    . As the respiratory minute volume increases, hyperventilation of pregnancy occurs, causing a decrease in alveolar CO2
  • Maternal Physiology in Pregnancy:Respiratory System
    This decrease lowers the maternal blood CO2 tension; however alveolar oxygen tension is maintained within normal limits.
    Maternal hyperventilation is considered a protective measure that prevents the fetus from the exposure to excessive levels of CO2.
    Because this decrease in FRC occurs without a concomitant change in dead space, there is little residual dilution and, therefore, presumably more efficient gas exchange.
  • Maternal Physiology in Pregnancy:Respiratory System
    Spirometry: the most common of the Pulmonary Function Tests(PFTs), measuring lung function, specifically the measurement of the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled.
    FEV1 (forced expiratory pressure in 1 second), 80-100% of average values are considered normal and is unchanged
    Peak Expiratory Flow: is the maximal flow (or speed) achieved during the maximally forced expiration initiated at full inspiration, measured in liters per minute, also unchanged
  • Lungs Function in Pregnancy
  • Lungs in late pregnancy
  • Maternal Physiology in Pregnancy:Respiratory System: Gas Exchange
    Hyperventilation leads to deceased PCO2
    Increases CO2 gradient between fetus and mother
    Chronic respiratory alkalosis
    Compensatory metabolic acidosis
    20-40% increase in maternal oxygen consumption
    Normal arterial blood gas values Ph= 7.4-7.45 PCO2= 28-32 PO2= 101-106 HCO3= 18-21
  • Maternal Physiology in Pregnancy
    Metabolism
    As the fetus and placenta grow and place increasing demands on the mother, phenomenal alterations in metabolism occur
    The most obvious physical changes are weight gain and altered body shape
    Weight gain is due not only to the uterus and its contents but also to increase breast tissue, blood and water volume in the form of extravascular and extracellular fluid
    Deposition of fat and protein and increased cellular water are added to the maternal stores
    The average weight gain during pregnancy is 12.5Kg.
    (23-25 lbs)
  • Maternal Physiology in Pregnancy
    During normal pregnancy, approximately 1000g of weight gain is attributable to protein
    Half of this is found in the fetus and the placenta, with the rest being distributed as uterine contractile protein, breast glandular tissue, plasma protein, and hemoglobin
    Total body fat increases during pregnancy, but the amount varies with total weight gain
    During the second half of pregnancy, plasma lipids increase , but triglycerides, cholesterol and lipoproteins decrease soon after delivery
    The ratio of low density lipoproteins to high density lipoproteins increases during pregnancy
  • Maternal Physiology in Pregnancy
    Body Water Metabolism
    Condition of chronic water overload
    Active Na+ and water retention
    1. Changes in osmoregulation
    2. Renin-angiotensin system
    Body water increase 6.5L 8.5L
    1. 1500 cc increase in blood volume
    2. RBC increase ~400cc
    Elevation of maternal CO
  • Maternal Physiology in Pregnancy
    Osmoregulation
    Na+ retention increases 900 mEq but serum Na+ decreases 3-4 mmol/l
    Plasma osmolality decreases 10 mOsm/kg
    Enhanced tubular reabsorption of Na+ secondary to aldosterone, estrogen and deoxycorticosterone
    Increased GFR and Atrial Natriuretic Peptide favor Na+ excretion
  • Maternal Physiology in Pregnancy
    Skeletal Changes: Calcium metabolism
    Maternal total calcium levels decline due to decreased albumin bound concentration
    Serum ionized level remains unchanged
    Increased intestinal absorption occurs in first trimester, actively transported across the placenta
    Maternal serum phosphate levels are unchanged
    PTH levels remain unchanged
    Elevated levels of vitamin D allow for increase Ca++ absorption
    Calcitonin levels rise to preserve maternal skeleton
  • Maternal Physiology in Pregnancy
    Skeletal and Postural Changes
    Lordosis of pregnancy~ progressive increase in anterior convexity of the lumbar spine, preserves center of gravity
    Ligaments of the symphysis and sacroiliac joints loosen during pregnancy due to relaxin
  • Maternal Physiology in Pregnancy
    Endocrine Changes
    Thyroid Physiology
    Euthyroid state
    Increase in thyroxine-binding globulin
    Decrease in circulating pool of extra-thyroidal iodide
    Slight thyromegaly
    Free T4 and Free T3 remain normal
    Small amounts of TRH /T4 cross the placenta
    Fetal thyroid active by 12 weeks gestation
  • Maternal Physiology in Pregnancy
    Endocrine Changes
    Adrenal function
    Increases in corticosteroid-binding globulin
    Increases in free cortisol
    Zona fasciculata is increased
    Marked increase in CRH from placental sources
    Delayed plasma clearance of cortisol due to renal changes
    Resetting of hypothalamic-pituitary sensitivity to cortisol feedback on ACTH production
  • Maternal Physiology in Pregnancy
    Endocrine Changes
    Pituitary gland enlarges due to proliferation of prolactin-secreting cells
    Enlargement makes it more susceptible to alterations in blood flow
    Prolactin levels are increased (ten times higher at term) to prepare breasts for lactation
  • Maternal Physiology in Pregnancy
    Endocrine Changes
    Pancreas and Fuel Metabolism
    Physiologic glucose intolerance to insure continuous transport of nutrients from mother to fetus
    Fasting hypoglycemia
    Postprandial hyperglycemia
    Hyperinsulinemia
  • Insulin Response after a Meal
  • Glucose Response after a Meal
  • Maternal Physiology in Pregnancy
    Fuel Metabolism
    Pregnant prolonged fasting
    Increased utilization of fat stores
    Lipolysis generates glycerol, fatty acids and ketones for gluconeogenesis and fuel
    More HPL, less insulin results in increased utilization of fat stores
    Maternal response to starvation hypoglycemia, hypoinsulinemia , hyperlipidemia, hyperketonemia
  • Maternal Physiology in Pregnancy
    Fuel Metabolism
    Maternal response to feeding
    Hyperglycemia
    Hyperinsulinemia
    Hyperlipidemia
    Resistance to insulin
    Insulin secretion increases throughout
    Insulin resistance increases to 50-80% in third trimester
    Borderline pancreas function leads to GDM
  • Maternal Physiology in Pregnancy
    Endocrine Changes
    Diabetogenic effects of pregnancy
    HPLlipolytic and anti-insulin( Cortisol Prolactin Estrogen and Progesterone
    Fetal glucose levels are 20 mg/dl less than maternal values
    Placental glucose transport is carrier mediated facilitated transport that is energy independent
  • Maternal Physiology in Pregnancy
    Fuel and Metabolism
    Lipids and lipoproteins increase in pregnancy
    Total cholesterol, LDL, HDL and triglycerides all increase
    Necessary as precursors for steroiodgenesis
    Does not appear to lead to atherosclerosis unless pre-existing hyperlipidemia
  • Placental Transport of Nutrients
  • Maternal Physiology in Pregnancy
    Integumental Changes
    Hyperpigmentation 90% of pregnancies
    Localized to areas of increased melanocytes
    Choasma of pregnancy 70% of women in all races
    Linea alba…Linea nigra
    Up to 30% of changes can persist
  • Maternal Physiology in Pregnancy
    Integumental Changes
    Hair Changes
    Mild hirsutism is common
    Excessive virilization should prompt investigation for androgen-secreting tumors
    Normal pregnancy increases amount of hair in anagen phase(growth)
    Postpartum, telogen effluvium may occur with increased amount of hair in resting phase which leads to loss
  • Maternal Physiology in Pregnancy
    Ocular Changes
    Increased thickness of the cornea secondary to fluid retention, this edema induces causing a 3% increase
    Affects contacts
    Decreased intraocular pressure
    Glaucoma improves
    Minimally decreases visual fields
  • Maternal Physiology in Pregnancy
    So you see there are extensive changes in maternal physiology that occur in pregnancy
    Be careful in interpretations of what are normal pregnancy changes, especially when parameters like lab values represent the non-pregnant state
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