Physiologic changes of pregnancy

1
Physiologic changes of pregnancy

• Nancy Thomas

2
Objectives

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

3
Organ systems

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

4
Cardiovascular system

• Total Body water
• Cardiac Output

5
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

6
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

7
Patients without overt anemia not given
supplementation

• Wide standard deviation

Williams 21ed
8
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

9
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

10
Cardiovascular system

• Total Body water
• Cardiac Output

11
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

12
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

13
Respiratory system

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

14
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

15
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.

16
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

17
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

18
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

19
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

20
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

21
Genital Tract

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

22
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.

23
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

24
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

25
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

26
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

27
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

28
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

29
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

30
Liver

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

31
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

32
Skin changes

• Chloasma or melasma gravidarum
• Striae
• Linea nigra

33
Melasma
34
Melasma
35
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

36
Striae

37
Striae

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

38
Linea nigra

39
Hyperpigmentation

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

40
The End-Go Tigers