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Physiology of Pregnancy for Undergraduates


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Physiology of pregnancy for medical undergrads.

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Physiology of Pregnancy for Undergraduates

  1. 1. Prepared by: Fadziyah zaira bte md fadzil, 4 th year, MBBS, Gef international medical school, Bangalore, India Physiology of Pregnancy
  2. 2. Introduction <ul><li>During pregnancy there is progressive anatomical and physiological changes not only confined to the genital organs but also all systems of the body. </li></ul><ul><li>Principally, this a phenomenon of maternal adaptation to the increasing demands of the growing fetus. </li></ul>
  3. 3. Genital organ changes <ul><li>Vulva </li></ul><ul><ul><li>Edematous and hyperaemic </li></ul></ul><ul><ul><li>Superficial varicosities may appear especially multipara. </li></ul></ul><ul><ul><li>Labia minora- pigmented, and hypertrophied. </li></ul></ul><ul><li>Vagina </li></ul><ul><ul><li>Hypertrophied </li></ul></ul><ul><ul><li>Edematous and more vascular. </li></ul></ul><ul><ul><li>Bluish discoloration of the mucosa (Jacquemier’s sign) </li></ul></ul><ul><ul><ul><li>Due to increased blood supply of the venous plexus. </li></ul></ul></ul><ul><ul><li>Length of anterior vaginal wall increased. </li></ul></ul>
  4. 4. Contd. <ul><li>Vaginal secretion </li></ul><ul><ul><li>Copious, thin and curdy white </li></ul></ul><ul><ul><ul><li>Due to marked exfoliated cells and bacteria. </li></ul></ul></ul><ul><ul><li>pH becomes acidic (3.5—6) </li></ul></ul><ul><ul><ul><li>Due to more conversion of glycogen into lactic acid by Lactobacillus acidophilic consequent on high estrogen level. </li></ul></ul></ul><ul><ul><ul><li>Prevents pathogenic infection </li></ul></ul></ul><ul><li>Vaginal cytology </li></ul><ul><ul><li>Preponderance of navicular cells (small intermediate cells with elongated nuclei) in cluster. </li></ul></ul>
  5. 5. Uterus <ul><li>At term </li></ul><ul><ul><li>900-1000gm at weight </li></ul></ul><ul><ul><li>35cm in length </li></ul></ul><ul><li>Changes occur at all parts of uterus </li></ul><ul><ul><li>Body </li></ul></ul><ul><ul><li>Isthmus </li></ul></ul><ul><ul><li>Cervix </li></ul></ul>
  6. 6. Uterus-cont <ul><li>Body of uterus </li></ul><ul><ul><li>There is increase in growth and enlargement of the body of the uterus. </li></ul></ul><ul><ul><li>Enlargement </li></ul></ul><ul><ul><li>Factor affecting the enlargement of the uterus. </li></ul></ul><ul><ul><ul><li>Change in the muscles </li></ul></ul></ul><ul><ul><ul><ul><li>Hypertrophy and hyperplasia-first half of pregnancy </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Stretching of muscle fibre beyond 20 wks of pregnancy. </li></ul></ul></ul></ul>
  7. 7. Uterus-cont <ul><ul><ul><li>Arrangement of the muscle fibres </li></ul></ul></ul><ul><ul><ul><ul><li>Outer longitudinal-hoodlike arrangement </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Intermediate-thickest and strongest, criss-cross arrangement </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Inner circular-scanty, sphincter-like arrangement. </li></ul></ul></ul></ul><ul><ul><ul><li>Simultaneous increase in number and size of supporting fibrous and elastic tissue. </li></ul></ul></ul><ul><ul><ul><li>Increased vascularity </li></ul></ul></ul><ul><ul><ul><ul><li>Ovarian artery carries more blood during pregnancy </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Markes spiraling of the arteries-maximum at 20 wks and then straigthen up and becomes dilated. </li></ul></ul></ul></ul>
  8. 8. Arrangement of muscle fibres during pregnancy
  9. 9. Uterus-cont <ul><ul><li>Shape of the uterus </li></ul></ul><ul><ul><ul><li>Pyriform </li></ul></ul></ul><ul><ul><ul><li>Globular – at 12 wks </li></ul></ul></ul><ul><ul><ul><li>Pyriform – by 28 wks </li></ul></ul></ul><ul><ul><ul><li>Spherical – beyond 36 wks </li></ul></ul></ul><ul><ul><li>Position </li></ul></ul><ul><ul><ul><li>Normal anteverted upto 8 weeks. </li></ul></ul></ul><ul><ul><ul><li>Erect afterwards </li></ul></ul></ul><ul><ul><li>Lateral obliquity </li></ul></ul><ul><ul><ul><li>Uterus enlarged and rotates to the right (dextrorotation) </li></ul></ul></ul>
  10. 10. Uterus-cont <ul><ul><li>Uterine peritoneum </li></ul></ul><ul><ul><ul><li>Maintains relation proportionately with the growing uterus. </li></ul></ul></ul><ul><ul><li>* Braxton-Hicks contraction </li></ul></ul><ul><ul><ul><li>spontaneous uterine contraction in pregnancy that occur from early weeks of pregnancy. </li></ul></ul></ul><ul><ul><ul><li>Irregular, infrequent, spasmodic and painless without any effect on dilatation of the cervix. </li></ul></ul></ul><ul><ul><li>Uterine endometrium </li></ul></ul><ul><ul><ul><li>Changes from non-pregnant uterus into decidua of pregnancy. </li></ul></ul></ul>
  11. 11. Uterus-cont <ul><li>Isthmus </li></ul><ul><ul><li>1 st trimester, isthmus hypertrophies and elongates to about 3 times its original length. </li></ul></ul><ul><ul><li>>12 weeks, it progressively unfolds from above downwards. </li></ul></ul><ul><ul><li>Circularly arranged muscle fibres in this region acts as sphincter that helps in retaining the fetus within the uterus. </li></ul></ul>
  12. 12. Uterus-cont <ul><li>Cervix </li></ul><ul><ul><li>Stroma: </li></ul></ul><ul><ul><ul><li>Hypertrophy and hyperplasia </li></ul></ul></ul><ul><ul><ul><li>Fluid accumulation </li></ul></ul></ul><ul><ul><ul><li>Increased vascularity-bluish colouration (Chadwick’s Sign) </li></ul></ul></ul><ul><ul><ul><li>Softening of the cervix (Goodell’s sign) </li></ul></ul></ul><ul><ul><li>Epithelium </li></ul></ul><ul><ul><ul><li>Marked proliferation of the endocervical mucosa with downward extension beyond squamocolumnar junction. </li></ul></ul></ul>
  13. 13. Uterus-cont <ul><ul><li>Secretion </li></ul></ul><ul><ul><ul><li>Copious and tenacious ( leucorrhea of pregnancy ) </li></ul></ul></ul><ul><ul><ul><li>Due to effect of progesterone </li></ul></ul></ul><ul><ul><ul><li>Mucus forms thick plug to seal cervical canal. </li></ul></ul></ul><ul><ul><li>Cervical length </li></ul></ul><ul><ul><ul><li>Unaltered but cervix becomes bulkier. </li></ul></ul></ul>
  14. 14. Advantage of having mucus plug formed during pregnancy
  15. 15. Other organs <ul><li>Fallopian tube </li></ul><ul><ul><li>Held vertical by side of the uterus </li></ul></ul><ul><ul><li>Total length is increased </li></ul></ul><ul><ul><li>Tube becomes congested </li></ul></ul><ul><ul><li>Epithelium is flattened </li></ul></ul><ul><ul><li>Patches of decidual reaction observed </li></ul></ul><ul><li>Ovary </li></ul><ul><ul><li>Persistent growth of the corpus luteum until 8 th wks and then regresses following decline of HCG secretion from the placenta. </li></ul></ul><ul><ul><li>It becomes colloid degeneration at 12 wks and later becomes calcified at term. </li></ul></ul>
  16. 16. Breasts <ul><li>Changes are best evident in primigravidae. </li></ul><ul><li>Size </li></ul><ul><ul><li>increased due to marked hypertrophy and proliferation of the ducts and the alveoli </li></ul></ul><ul><li>Nipples and areola </li></ul><ul><ul><li>Larger, erect, deeply pigmented </li></ul></ul><ul><ul><li>Montgomery tubercles -hypertrophied sebaceous glands that is visible in the areola during pregnancy. </li></ul></ul><ul><ul><li>Secondary areola - outer zone of less marked and irregular pigmented area that appear at 2 nd trimester. </li></ul></ul>
  17. 17. Breast changes Pigmented, erect nipple Montgomery tubercles Secondary areola
  18. 18. <ul><li>Secretion </li></ul><ul><ul><li>Can be squeezed out at 12 th wks which is sticky at first. </li></ul></ul><ul><ul><li>16 th wks-it becomes thick and yellowish. </li></ul></ul><ul><ul><li>Later-colostrum may be expressed from the nipples. </li></ul></ul>
  19. 19. Cutaneous changes <ul><li>Face </li></ul><ul><ul><li>Chloasma gravidarum/pregnancy mask </li></ul></ul><ul><li>Abdomen </li></ul><ul><ul><li>Linea nigra - brownish black pigmented area in the midline from xiphisternum to symphysis pubis. </li></ul></ul><ul><ul><li>Striae gravidarum – slightly depressed linear marks with varing length and breadth. </li></ul></ul><ul><ul><li>Striae albicans- glistening white scar tissue after delivery </li></ul></ul>
  20. 20. Chloasma gravidarum
  21. 21. Linea Nigra
  22. 22. Striae gravidarum
  23. 23. Weight gain <ul><li>Early wks pt may lose weight because of vomiting. </li></ul><ul><li>Subsequent months, the weight gain is progressive until last one or two wks where weights becomes static. </li></ul><ul><li>Total weight gain during course of single pregnancy for healthy woman is 11 kg. </li></ul><ul><li>1kg rise during first trimester, 5kg each during subsequent trimesters. </li></ul>
  24. 24. Weight gain-cont <ul><li>Retention of electrolytes- sodium, potassium and chlorides. </li></ul><ul><li>Retention of Na+ causes water retention. </li></ul><ul><li>At term, nearly 6.5liters water is retained. </li></ul><ul><li>Importance of weight checking </li></ul><ul><ul><li>Rapid gain in weight of more than 0.5kg a week/>2kg a month is maybe an early manifestation of pre-eclampsia and need for careful supervision. </li></ul></ul><ul><ul><li>Stationary / falling weight- IUGR/intrauterine death of fetus. </li></ul></ul>
  25. 25. Body water metabolism <ul><li>Pregnancy is a state of hypervolemia. </li></ul><ul><li>Causes of sodium retention and volume overload are </li></ul><ul><ul><li>Changes in osmoregulation </li></ul></ul><ul><ul><li>Increased estrogen and progesterone </li></ul></ul><ul><ul><li>Increased renin angiotensin activity </li></ul></ul><ul><ul><li>Increased aldosterone </li></ul></ul><ul><ul><li>Atrial natriuretic peptide. </li></ul></ul><ul><li>Resetting of osmotic threshold for thirst and ADH secretion. </li></ul><ul><li>Increased water intake due to lowered osmotic threshold for thirst causes polyuria in early pregnancy. </li></ul>
  26. 26. Hematological changes <ul><li>Blood volume </li></ul><ul><ul><li>Markedly raised </li></ul></ul><ul><ul><li>Increased from 6 th wks, expands rapidly tp maximum 40-50% above nonpregnant level at 30-32 wks. </li></ul></ul><ul><li>Plasma volume </li></ul><ul><ul><li>Increases to 1.25liters </li></ul></ul><ul><li>RBC and Hb </li></ul><ul><ul><li>RBC volume increased 20-30% </li></ul></ul><ul><ul><li>Total volume increase: 350ml </li></ul></ul>
  27. 27. Hematological changes <ul><li>Hemodilution occur during pregnancy and fall in Hb concentration. </li></ul><ul><li>Advantage of hemodilution during pregnancy </li></ul><ul><ul><li>Diminished blood viscosity thus optimum gaseous exchange between mama and baby </li></ul></ul><ul><ul><li>Protection from the mother against the adverse effects of blood loss during pregnancy. </li></ul></ul>
  28. 28. Hematological changes <ul><li>Leucocytes </li></ul><ul><ul><li>Neutrophilic leucocytosis </li></ul></ul><ul><ul><li>Due to increased estrogen and cortisol </li></ul></ul><ul><li>Total protein </li></ul><ul><ul><li>Increases from normal 180gm to 230gm at term </li></ul></ul><ul><ul><li>A:G ratio is diminished to 1:1 </li></ul></ul><ul><li>Blood coagulation factor </li></ul><ul><ul><li>Pregnancy is hypercoagulable state. </li></ul></ul><ul><ul><li>Fibrinogen level is raised by 50%  4-fold rise in ESR </li></ul></ul>
  29. 29. Heart and circulation <ul><li>Anatomical changes </li></ul><ul><ul><li>Heart is pushed upwards and outwards </li></ul></ul><ul><li>CO </li></ul><ul><ul><li>Increased from 5 th wks of pregnancy reaches peak 40-50% at 30-34wks. </li></ul></ul><ul><ul><li>Caused by </li></ul></ul><ul><ul><ul><li>Increased blood volume </li></ul></ul></ul><ul><ul><ul><li>To meet additional O2 required due to high metabolic activity during pregnancy </li></ul></ul></ul><ul><li>BP </li></ul><ul><ul><li>Decreased due to decreased vascular resistance </li></ul></ul>
  30. 30. Heart and circulation <ul><li>Venous pressure </li></ul><ul><ul><li>Femoral venous pressure is markedly increased due to pressure exerted by gravid uterus on the common iliac veins. </li></ul></ul><ul><li>Central hemodynamics </li></ul><ul><ul><li>No significant change in CVP, MAP, and PCWP. </li></ul></ul><ul><li>Postural hypotension </li></ul><ul><ul><li>Compression of gravid uterus to IVC and failed collateral circulation (parasternal and azygos veins) </li></ul></ul>
  31. 31. Heart and circulation <ul><li>Regional distribution of blood flow </li></ul><ul><ul><li>Uterine blood flow increased to 750ml/min near term. </li></ul></ul><ul><ul><li>Pulmonary BF increased by 2500ml/min </li></ul></ul><ul><ul><li>Renal BF increased by 400ml/min </li></ul></ul><ul><ul><li>Explains flushing, sweating or stuffy nose in pregnancy. </li></ul></ul>
  32. 32. Metabolic changes <ul><li>General metabolism </li></ul><ul><ul><li>increased due to needs of growing fetus </li></ul></ul><ul><ul><li>BMR increased to extent of 30% higher </li></ul></ul><ul><li>Protein metabolism </li></ul><ul><ul><li>Positive nitrogenous balance throughout pregnancy </li></ul></ul><ul><ul><li>Anabolism! </li></ul></ul><ul><li>Carbohydrate metabolism </li></ul><ul><ul><li>Insulin secretion increased </li></ul></ul><ul><ul><li>Sensitivity of insulin receptor reduced </li></ul></ul><ul><ul><li>To ensure continous supply of glucose to fetus </li></ul></ul>
  33. 33. Metabolic changes <ul><li>Fat metabolism </li></ul><ul><ul><li>3-4kg fat stored at abdoment,breast, hips and thighs. </li></ul></ul><ul><li>Lipid metabolism </li></ul><ul><ul><li>HDL level increased by 15% </li></ul></ul><ul><ul><li>LDL utilised for placental steroid synthesis. </li></ul></ul><ul><li>Iron metabolism </li></ul><ul><ul><li>Pregnancy is an iron deficiency state </li></ul></ul><ul><ul><li>Absorption from gut is increased but lost along the routes, to placenta and during delivery. </li></ul></ul><ul><ul><li>Serum iron and ferritin will fall if supplementation is not given. </li></ul></ul>
  34. 34. Systemic changes <ul><li>Respiratory system </li></ul><ul><ul><li>Breathing becomes diaphragmatic </li></ul></ul><ul><ul><li>Transverse diameter of chest expends by 2 cm </li></ul></ul><ul><ul><li>Chest circumference increased by 5-7cm </li></ul></ul><ul><ul><li>Mucosa of URT shows congestion </li></ul></ul><ul><ul><li>Hyperventilation occur due to increased tidal volume and progesterone acting at the respiratory center. </li></ul></ul><ul><li>Acid base balance </li></ul><ul><ul><li>PCO2 fall, PO2 rises- facilitate transfer of gases between mam and baby </li></ul></ul><ul><ul><li>pH rises- respiratory alkalosis due to high maternal O2 consumption and fetal demand. </li></ul></ul>
  35. 35. Systemic changes <ul><li>Urinary system </li></ul><ul><ul><li>Dilatation of ureter and renal pelvis </li></ul></ul><ul><ul><li>Kidney enlarges by 1cm </li></ul></ul><ul><ul><li>Renal plasma flow increased by 50-75% </li></ul></ul><ul><li>Alimentary system </li></ul><ul><ul><li>Muscle tone and motility of entire GI tract are diminished due to increased progesterone level </li></ul></ul><ul><ul><li>Cardiac sphincter relaxes  chemical esophagitis and heart burn </li></ul></ul><ul><ul><li>Diminished gastric secretion </li></ul></ul>
  36. 36. Systemic changes <ul><li>Liver and gallbladder </li></ul><ul><ul><li>Functions are depressed except LFT serum levels. </li></ul></ul><ul><li>Nervous system </li></ul><ul><ul><li>Psychological changes-nausea, sleeplessness </li></ul></ul><ul><ul><li>Postpartum blues, depression or psychosis </li></ul></ul>
  37. 37. Summary <ul><li>There is various changes happening in a pregnant mother, not only at specific organs, but also systemically. </li></ul><ul><li>It is important to know these changes so we as doctors should assure them that the changes are normal whenever they have doubt about what’s happening to their own body. </li></ul>