Physiologic changes during pregnancy

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Physiologic changes during pregnancy
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Objectives

• Symptoms and physical findings of each organ
  system
• Physiologic versus pathologic changes
• Diagnostic tests and interpretations during
  physiological changes

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Organ systems

• Cardiovascular system
• Pulmonary system
• Genital tract
• Urinary system
• Endocrine system
• Gastrointestinal Tract
• Skin

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Cardiovascular system

• Total Body water
• Cardiac Output

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Total body water

• Increases 6-8 L
• Increases by 40
• Normal body water
• 2/3 intracellular
• 1/3 extracellular
• ¾ interstitial
• ¼ intravasular
• 2/3 increase is extravascular

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Physiologic anemia of pregnancy

• Physiologic intravascular change
• Plasma volume increases 50-70
• Beginning by the 6th wk
• RBC mass increases 20-35
• Beginning by the 12th wk
• Disproportionate increase in plasma volume over
  RBC volume----Hemodilution
• Despite erythrocyte production there is a
  physiologic fall in the hemoglobin and hematocrit
  readings

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Patients without overt anemia not given
supplementation
concentration Non preg 1st Tri 2nd Tri 3rd Tri deliv
HB 13.0 12.2 10.9 11.0 12.4
Serum iron 90.0 106.5 75.3 56.0 57.1
Serum Ferritin 63.0 97.4 22.2 14.7 27.6

• Wide standard deviation

Williams 21ed
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Iron deficiency anemia

• With erythropoiesis of pregnancy, iron
  requirements increase.
• Because large amounts of iron may not be
  available from body stores and may not be in the
  diet
• Supplementation is recommended to prevent iron
  deficiency anemia
• At term, Hemoglobin less than 10.0 is usually due
  to iron deficiency anemia rather than the
  hemodilution of pregnancy

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Normal Iron Requirements

• Total body iron content average in normal adult
  females is 2gm
• Iron requirement for normal pregnancy is 1 gm
• 200 mg is excreted
• 300 mg is transferred to fetus
• 500 mg is need for mom
• Total volume of RBC inc is 450 ml
• 1 ml of RBCs contains 1.1 mg of iron
• 450 ml X 1.1 mg/ml 500 mg
• Daily average is 6-7 mg/day
• Small intervals between pregnancies are most
  concerning

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Cardiovascular system

• Total Body water
• Cardiac Output

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Cardiac output (COHR X SV)

• Begins to increase by the 5th wk
• Rise of 40 by 20-24 wks
• Initial increase is a function of
• The increase in heart rate
• Reduced systemic vascular resistance
• By 10- 20 wks the increase in CO is reflected
  mainly by the increase in SV
• The notable increase in plasma volume or preload
  contributes to the increase SV
• As pregnancy advances to term, the HR continues
  to increase but the SV falls to close to normal
  levels, this accounts for the fall in CO to near
  non-pregnant levels at term

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Interpretation of tests during pregnancy

• CXR
• Elevation of diaphragm
• Heart to be displaced to the left and upward
• Increase in the cardiac silhouette
• benign pericardial effusion
• Echocardiogram
• Increased left ventricular wall mass
• Increased end diastolic dimensions
• Increase in EDV and therefore inc in SV
• Electrocardiogram
• Slight left axis deviation

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Respiratory system

• Mechanical
• diaphragm
• Consumption
• Increase in needed oxygen
• Stimulation
• Progesterone stimulation

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Respiratory

• Mechanical
• Diaphragm rises 4 cm
• Less negative intrathoracic pressure
• Dec FRC-Functional Residual Capacity
• volume after passive expiration
• Dec ERV-Expiratory Reserve Volume
• max volume expired after expiration
• Dec RV-Residual Volume
• volume after max expiration
• No impairments in diaphragmatic or thoracic
  muscle motion
• Lung compliance remains unaffected

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Respiratory

• Consumption
• O2 consumption Increases 15-20
• 50 of this increase is required by the uterus
• Despite increase in oxygen requirements, with the
  increase in Cardiac Output and increase in
  alveolar ventilation oxygen consumption exceeds
  the requirements.
• Therefore, arteriovenous oxygen difference falls
  and arterial PCO2 falls.

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Respiratory

• Stimulation
• Progesterone is known to directly stimulate
  ventilation
• Progesterone increases the sensitivity of the
  respiratory centers to CO2
• Also, it is thought to reduce total pulmonary
  resistance

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Respiratory

• Minute ventilation RR X Tidal volume
• Tidal Volume-increases
• Volume of air Inspired and expired with each
  breath
• Minute ventilation-increases
• Volume inspired or expired in 1 min
• RR- remains unchanged
• Vital capacity-remains unchanged
• Max volume that can be forcibly inspired after
  max expiration

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Physiologic changes

• Dyspnea-increase in desire to breathe
• 70 of pregnant women experience this
• Occurs during 1st trimester without mechanical
  factors
• No change on PFTs
• The lower PCO2 then paradoxically causes dyspnea
• The marked change or marked decline in PCO2
  results in the sensation of dyspnea

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Genital Tract

• Increased vascularity and hyperemia
• Vagina
• Perineum
• Vulva
• Increased secretions
• Characteristic violet color of the vagina
• Chadwicks sign
• Increased length to the vaginal wall
• Hypertrophy of the papillae of the vaginal mucosa

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Genital Tract

• Uterine hypertrophy of the myocytes
• Hypertrophy can cause venous compression
• Can result in fall in venous return
• Furthermore a fall in CO
• Physiologic compensation
• Rise in peripheral resistance to minimize fall in
  blood pressure

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Genital Tract

• Without Physiologic compensation
• Supine hypotensive syndrome can occur with a
  gravid uterus
• Symptoms-Nausea, dizziness, syncope
• Can be relieved with position changes

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Gravid uterus has limited autoregulation

• Uterine blood flow is Increased 100 ml/min to
  1200 ml/min
• Because uterine vessels are maximally dilated
  little autoregulation can occur to improve flow
  during perfusion pressure changes
• When maternal Cardiac output declines, blood flow
  is shifted away from the uteroplacental
  circulation to the maternal brain, kidney and
  heart.

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Urinary System-Dilation

• Calyces, renal pelves, and ureters undergo marked
  dilatation
• More prominent on the right
• Partial obstruction of the ureters can occur at
  the pelvic brim
• Progesterone produces smooth muscle relaxation
  which is thought to cause the relaxation noted

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Urinary System-inc GFR

• GFR and renal plasma flow increases 40 by
  mid-gestation
• Plateaus, then remains unchanged until term
• Elevated GFR is reflected in the lower serum
  levels of creatinine and blood urea nitrogen
• NL GFR 120-160 ml/min

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Urinary System-Proteinuria

• Normally not evident
• Average is 115 mg/day
• 260 mg/day is in 95 percent confidence limit
• Therefore, our 300 mg screen would exceed most
  normal variations

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Endocrine

• Normal pregnancy physiology shows
• lower lows and higher highs
• Postprandial hyperglycemia
• To ensure sustained glucose levels for fetus
• Accelerated starvation
• Early switch from glucose to lipids for fuels
• Insulin resistance promotes hyperglycemia
• Resistance-Reduced peripheral uptake of glucose
  for a given dose of insulin
• Mild fasting hypoglycemia occurs with elevated
  FFA, triglycerides,and cholesterol

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Insulin resistance

• Anti-insulin environment is aided by
• placental lactogen
• Like growth hormone
• Increases lipolysis and FFA
• Increases tissue resistance to insulin
• Increased unbound cortisol
• Estrogen and Progesterone may also exert some
  anti-insulin effects

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Thyroid

• Estrogen stimulates Increase in TBG
• Total T3 and T4 are increased
• However the active hormones remains unchanged
• hCG stimulates thyroid
• TSH is reduced
• Iodine deficient state
• Due to Increased renal clearance
• To rule out pathologic changes
• Early in pregnancy TSH can be used
• Later free T4 is needed

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Gastrointestinal Tract

• Displacement of the stomach and intestines
• Appendix can be displaced to reach the right
  flank
• Gastric emptying and intestinal transit times are
  delayed secondary to hormonal and mechanical
  factors
• Pyrosis is common due to the reflux of secretions
• Vascular swelling of the gums
• Hemorrhoids due to elevated pressure in veins

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Liver

• Liver morphology unchanged
• Lab Tests similar to liver disease
• Alkaline phosphatase doubles
• AST, ALT, GGT and bilirubin are slightly lower
• Decreased plasma albumin

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Gallbladder

• Impaired contraction
• High residual volumes
• Promotion of stasis
• Stasis associated with increased cholesterol
  saturation of pregnancy, supports predisposition
  of stones
• Intrahepatic cholestasis
• Retained bile salts-pruritus gravidarum

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Skin changes

• Chloasma or melasma gravidarum
• Striae
• Linea nigra

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Melasma
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Melasma
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Melasma

• Also known as the mask of pregnancy
• More common in dark skin people
• More pronounced in the summer
• Fades a few months after delivery
• Repeated pregnancy can intensify
• Can occur in normal non-pregnant women with
  harmless hormonal imbalances or women on OCPs or
  depo

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Striae

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Striae

• Reddish slightly depressed
• Breasts, thighs, and abdomen
• In future pregnancies they appear as glistening,
  silver lines

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Linea nigra

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Hyperpigmentation

• Melasma and linea nigra
• Estrogen and progesterone
• Some melanocyte stimulating effect

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The End