physiologicalchangesduringpregnancy-220612062159-e992f482.pptx

Obg

1. Physiological Changes During Pregnancy Dr.vinothkumar M.S OBG Assistant professor

2. Introduction During pregnancy there is progressive anatomical , physiological and biochemical change not only confined to the genital organs but also to all systems of the body. This is principally a phenomenon of maternal adaptation to the increasing demands of the growing fetus .

3. GENITAL ORGANS BREASTS CUTANEOUS CHANGES WEIGHT GAIN BODY WATER METABOLISM HEMATOLOGICAL CHANGES CARDIOVASCULAR SYSTEM METABOLIC CHANGES SYSTEMIC CHANGES

4. GENITAL ORGANS

5. GENITAL ORGANS VULVA: Vulva becomes edematous and more vascular . Superficial varicosities ( multiparae ). Labia minora ( pigmented and hypertrophied). VAGINA: Vaginal walls becomes hypertrophied, edematous and more vascular . Increased blood supply of the venous plexus surrounding the walls gives the bluish coloration of the mucosa ( Jacquemier’s sign ). The length of the anterior vaginal wall is increased.

6. Secretion : The secretion becomes copious, thin and curdy white , due to marked exfoliated cells and bacteria. The pH becomes acidic (3.5–6) due to more conversion of glycogen into lactic acid by the Lactobacillus acidophilus consequent on high estrogen level. The acidic pH prevents multiplication of pathogenic organisms . Cytology : There is preponderance of navicular cells in cluster and plenty of lactobacillus .

7. UTERUS There is enormous growth of the uterus during pregnancy. The uterus which in nonpregnant state weighs about 60 gm , cavity of 5–10 mL and measures about 7.5 cm in length . At term , weighs 900–1000 g and measures 35 cm in length . The capacity is increased by 500–1000 times. Changes occur in all the parts of the uterus—body, isthmus and cervix.

8. BODY OF THE UTERUS: There is increase in growth and enlargement of the body of the uterus. Enlargement: The enlargement of the uterus is affected by the following factors: Changes in the muscles (1) Hypertrophy and hyperplasia (New muscle fibers – estrogen & progesterone – up to 12week). (2) Stretching (beyond 20weeks – wall become thinner at term – 1.5cm ).

9. Arrangement of the muscle fibers : Three distinct layers of muscle fibers are evident: (1) Outer longitudinal (continuous – round ligaments). (2) Inner circular (scanty – sphincter like arrangement). (3) Intermediate (thickest & strongest – crisscross).

10. Apposition of two double curve muscle fibers give the figure of ‘8’ form. Thus, when the muscles contract , they occlude the blood vessels running through the fibers and hence called living ligature .

11. Vascular system Nonpregnant state – blood supply to the uterus is mainly through the uterine and least through the ovarian . Pregnant state , the latter carries as much the blood as the former. There is marked spiralling of the arteries , reaching the maximum at 20 weeks; thereafter, they straighten out.

12. Doppler velocimetry has shown uterine artery diameter becomes double and blood flow increases by eight fold at 20 weeks of pregnancy. This vasodilatation is mainly due to estradiol and progesterone .

13. Veins become dilated and are valveless . Numerous lymphatic channels open up. The vascular changes are most pronounced at the placental site. The uterine enlargement is not a symmetrical one. The fundus enlarges more than the body .

14. Weight: The increase in weight is due to the increased growth of the uterine muscles, connective tissues and vascular channels . Relation : Shape — Nonpregnant pyriform shape is maintained in early months. It becomes globular at 12 weeks. As the uterus enlarges, the shape once more becomes pyriform or ovoid by 28 weeks and changes to spherical beyond 36th week.

15. Position: Normal anteverted position is exaggerated upto 8 weeks. Thus, the enlarged uterus may lie on the bladder rendering it incapable of filling, clinically evident by frequency of micturition . Multiparae with lax abdominal wall , there is a tendency of anteversion . Primigravidae with good tone of the abdominal muscles , it is held firmly against the maternal spine.

16. Lateral obliquity: As the uterus enlarges to occupy the abdominal cavity, it usually rotates on its long axis to the right ( dextrorotation ). This is due to the occupation of the rectosigmoid in the left posterior quadrant of the pelvis. This makes the anterior surface of the uterus to turn to the right and brings the left cornu closer to the abdominal wall . The cervix, as a result , is deviated to the left side ( levorotation ) bringing it closer to the ureter .

17. Contractions ( Braxton-Hicks ): During pregnancy, uterus undergoes spontaneous contraction. This can be felt during bimanual palpation in early weeks or during abdominal palpation . The contractions are irregular , infrequent , spasmodic and painless without any effect on dilatation of the cervix. The patient is not conscious about the contractions.

18. Braxton-Hicks Near term , the contractions become frequent with increase in intensity so as to produce some discomfort to the patient. Ultimately, it merges with the painful uterine contractions of labor . In abdominal pregnancy , Braxton-Hicks contraction is not felt .

19. During contraction there is complete closure of the uterine veins with partial occlusion of the arteries in relation to intervillous space resulting in stagnation of blood in the space. This diminishes the placental perfusion , causing transient fetal hypoxia which leads to fetal bradycardia coinciding with the contraction.

20. ISTHMUS During the first trimester, isthmus hypertrophies and elongates to about 3 times its original length. It becomes softer.

21. CERVIX Stroma : There is hypertrophy and hyperplasia of the elastic and connective tissues. Fluids accumulate inside and in between the fibers . Vascularity is increased specially beneath the squamous epithelium of the portio vaginalis which is responsible for its bluish coloration. Chadwick’s Sign. Goodell’s Sign. Mucus Plug.

22. Epithelium: There is marked proliferation of the endocervical mucosa with downward extension beyond the squamocolumnar junction. This gives rise to clinical appearance of ectopy (erosion) cervix.

23. Sometimes, the squamous cells also become hyperactive and the mucosal changes simulate basal cell hyperplasia or cervical intraepithelial neoplasia (CIN). These changes are hormone induced ( estrogen ) and regress spontaneously after delivery.

24. Secretion: The secretion is copious and tenacious-physiological leucorrhea of pregnancy. This mucous is rich in immunoglobulins and cytokines . The mucus not only fills up the glands but forms a thick plug effectively sealing the cervical canal . Microscopic examination shows fragmentation or crystallization (beading) due to progesterone effect.

25. Anatomical: The length of the cervix remains unaltered but becomes bulky. The cervix is directed posteriorly but after the engagement of the head, directed in line of vagina. There is no alteration in the relation of the cervix. Variable amount of effacement is noticed near term in primigravidae . In multiparae , the canal is slighly dilated .

26. FALLOPIAN TUBE: The total length is somewhat increased . The tube becomes congested . Muscles undergo hypertrophy .

27. OVARY: The growth and function of the corpus luteum reaches its maximum at 8th week when it measures about 2.5 cm and becomes cystic. It looks bright orange , later on becomes yellow and finally pale . Regression occurs following decline in the secretion of human chorionic gonadotropin ( hCG ) from the placenta.

28. Hormones- estrogen and progesterone secreted by the corpus luteum maintain the environment for the growing ovum before the action is taken over by the placenta. These hormones not only control the formation and maintenance of decidua of pregnancy, but also inhibit ripening of the follicles. Thus both the ovarian and uterine cycles of the normal menstruation remain suspended.

29. Decidual reaction: There may be patchy sheet of decidual cells on the outer surface of the ovary. These are metaplastic changes due to high hormonal stimulation.

30. BREASTS

31. SIZE: Increased size of the breasts becomes evident even in early weeks. There is also hypertrophy of the connective tissue stroma . Myoepithelial cells become prominent . Vascularity is increased which results in appearance of bluish veins running under the skin. “Axillary tail” ( prolongation of the breast tissue under cover of the pectoralis major ) – becomes enlarged and painful .

32. NIPPLES AND AREOLA: The nipples become larger , erectile and deeply pigmented. Variable number of sebaceous glands (5–15) which remain invisible in the nonpregnant state in the areola, become hypertrophied and are called Montgomery’s tubercles . Those are placed surrounding the nipples. Their secretion keeps the nipple and the areola moist and healthy . An outer zone of less marked and irregular pigmented area appears in second trimester and is called secondary areola .

33. SECRETION: Secretion ( colostrum ) can be squeezed out of the breast at about 12th week which at first becomes sticky. Later on, by 16th week, it becomes thick and yellowish .

34. CUTANEOUS CHANGES

35. CUTANEOUS CHANGES PIGMENTATION- Face ( chloasma gravidarum or pregnancy mask ): It is an extreme form of pigmentation around the cheek , forehead and around the eyes . It may be patchy or diffuse; disappears spontaneously after delivery. Abdomen: Linea nigra . Striae gravidarum . Striae albicans .

36. Linea nigra : It is a brownish black pigmented area in the midline stretching from the xiphisternum to the symphysis pubis. Striae gravidarum : These are slightly depressed linear marks with varying length and breadth found in pregnancy. They are predominantly found in the abdominal wall below the umbilicus, sometimes over the thighs and breasts.

37. Striae albicans : These stretch marks represent the scar tissues in the deeper layer of the cutis. Initially, these are pinkish but after the delivery, the scar tissues contract and obliterate the capillaries and they become glistening white in appearance and are called Striae albicans

38. OTHER CUTANEOUS CHANGES: These include vascular spider and palmar erythema which are due to high estrogen level. Mild degrees of hirsutism may be observed and in puerperium the excess hair is lost.

39. WEIGHT GAIN

40. WEIGHT GAIN The total weight gain during the course of a singleton pregnancy for a healthy woman averages 11 kg (24 lb ) This has been distributed to 1 kg in first trimester and 5 kg each in second and third trimester. The total weight gain at term is distributed approximately as follows:

41. During pregnancy, there is variable amount of retention of electrolytes: Sodium (1000 mEq ), Potassium (10 g) and Chlorides . The sodium is osmotically active and partially controls the distribution of water in various compartments of the body. Causes of increased sodium retention during pregnancy are: (1) increased estrogen and progesterone (2) increased aldosterone consequent on the activation of the renin-angiotensin system . (3) due to increased antidiuretic hormone . The amount of water retained during pregnancy at term is 6.5 liters .

42. The increased accumulation of fluid in the tissue spaces mainly below the uterus is due to: (1 ) diminished colloid osmotic tension due to hemodilution driving the fluid out of the vessels and (2 ) increased venous pressure of the inferior extremities.

43. Importance of weight checking: Rapid gain in weight of more than 0.5 kg (1 lb ) a week or more than 2 kg (5 lb ) a month in later months of pregnancy may be the early manifestation of pre- eclampsia and need for careful supervision. Stationary or falling weight may suggest intrauterine growth retardation or intrauterine death of fetus .

44. BODY WATER METABOLISM

45. BODY WATER METABOLISM The amount of water retained at term is about 6.5 liters . The water content of the fetus , placenta and amniotic fluid is about 3.5 liters . Pregnancy is a state of hypervolemia . There is active retention of sodium (900 mEq ), potassium (300 mEq ) and water.

46. The important causes of sodium retention and volume overload are: Changes in osmoregulation Increased estrogen and progesterone Increase in reninangiotensin activity Increased aldosterone, deoxycorticosterone Increase in water intake due to lowered osmotic threshold for thirst causes polyuria in early pregnancy.

47. HEMATOLOGICAL CHANGES

48. HEMATOLOGICAL CHANGES BOOD VOLUME PLASMA VOLUME RBC AND HEMOGLOBIN LEUKOCYTES and IMMUNE SYSTEM TOTAL PROTEIN BLOOD COAGULATION FACTORS

49. BLOOD VOLUME During pregnancy there is increased vascularity of the enlarging uterus with the interposition of uteroplacental circulation. The activities of all the systems are increased . Blood volume is markedly raised during pregnancy. All the constituents of blood are affected with increased blood volume. The blood volume starts to increase from about 6th week , expands rapidly thereafter to maximum 40–50% above the nonpregnant level at 30–32 weeks. The level remains almost static till term.

50. PLASMA VOLUME It starts to increase by 6 weeks and it plateaus at 30 weeks of gestation. The rate of increase almost parallels to that of blood volume but the maximum is reached to the extent of 50%. Total plasma volume increases to the extent of 1.25 liters . The increase is greater in multigravida, in multiple pregnancy and with large baby.

51. RBC AND HEMOGLOBIN The RBC mass is increased to the extent of 20–30%. The total increase in volume is about 350 mL . This increase is regulated by the increased demand of oxygen transport during pregnancy. RBC mass begins to increase at about 10 weeks and continue till term without plateauing. Iron supplementation increases the RBC mass by 30 %. Reticulocyte count increases by 2%. Erythropoietin level is raised.

52. The disproportionate increase in plasma and RBC volume produces a state of hemodilution ( fall in hematocrit ) during pregnancy. The advantages of relative hemodilution are: Diminished blood viscosity ensures optimum gaseous exchange between the maternal and fetal circulation. This is facilitated by lowered oxygen affinity of maternal red cells observed in later half of pregnancy. It protects the woman against the adverse effects of supine and erect posture. Protection of the mother against the adverse effects of blood loss during delivery

53. LEUKOCYTES and IMMUNE SYSTEM Neutrophilic leucocytosis occurs to the extent of 8000/mm3 and even to 20,000/cu.mm in labor . The increase may be due to rise in the levels of estrogen and cortisol.

54. TOTAL PROTEIN Total plasma protein increases from the normal 180 g ( nonpregnant ) to 230 g at term.

55. BLOOD COAGULATION FACTORS Pregnancy is a hypercoagulable state. Fibrinogen level is raised by 50% from 200–400 mg/ dL in nonpregnant to 300–600 mg/ dL in pregnancy . As a result Erythrocyte sedimentation rate (ESR) gives a much higher value ( four fold increase ) during pregnancy. Gestational thrombocytopenia may be due to increased platelet consumption.

56. To be continued…

57. CARDIOVASCULAR SYSTEM

58. CARDIOVASCULAR SYSTEM ANATOMICAL CHANGES: Due to elevation of the diaphragm consequent to the enlarged uterus, the heart is pushed upwards and outwards with slight rotation to left.

59. Abnormal clinical findings The apex beat is shifted to the 4th intercostal space about 2.5 cm outside the midclavicular line. A systolic murmur may be audible in the apical or pulmonary area. This is due to decreased blood viscosity and torsion of the great vessels. A continuous hissing murmur ( audible over the tricuspid area in the left second and third intercostal spaces called the “ mammary murmur ”).

60. Doppler echocardiography shows an increase in the left ventricular end diastolic diameters. ECG reveals normal pattern except evidences of left axis deviation .

61. CARDIAC OUTPUT The cardiac output (CO) starts to increase from 5th week of pregnancy, reaches its peak 40–50% at about 30–34 weeks. CO is lowest in the sitting or supine position and highest in the right or left lateral or knee chest position . Cardiac output increases further during labor (+50%) and immediately following delivery (+70%). MAP also rises .

62. The increase in CO is caused by: Increased blood volume To meet the additional O2 required due to increased metabolic activity during pregnancy.

63. BLOOD PRESSURE Systemic vascular resistance (SVR) decreases (–21%) due to the smooth muscle relaxing. Inspite of the large increase in cardiac output, the maternal BP (BP = CO × SVR) is decreased due to decrease in SVR. There is overall decrease in diastolic blood pressure (BP) and mean arterial pressure ( MAP) by 5–10 mm Hg .

64. VENOUS PRESSURE Antecubital venous pressure remains unaffected . Femoral venous pressure is markedly raised specially in the later months. The femoral venous pressure is raised from 8–10 cm of water in nonpregnant state to about 25 cm of water during pregnancy in lying down position and to about 80–100 cm of water in standing position. This explains the fact that the physiological edema of pregnancy subsides by rest alone. Distensibility of the veins and stagnation of blood in the venous system explain the development of edema , varicose veins, piles and deep vein thrombosis.

65. CENTRAL HEMODYNAMICS No significant change in CVP, MAP and PCWP though there is increase in blood volume, cardiac output and heart rate. The reasons are: There is significant fall in SVR, pulmonary vascular resistance (PVR) and colloidal osmotic pressure.

66. SUPINE HYPOTENSION SYNDROME ( POSTURAL HYPOTENSION ) The gravid uterus produces a compression effect on the inferior vena cava when the patient is in supine position. This results in production of hypotension, tachycardia and syncope. The normal blood pressure is quickly restored by turning the patient to lateral position .

67. REGIONAL DISTRIBUTION OF BLOOD FLOW: Uterine blood flow is increased from 50 mL/min in non-pregnant state to about 750 mL near term. The increase is due to the combined effect of uteroplacental and fetoplacental vasodilatation.

68. Pulmonary blood flow (normal 6000 mL /min) is increased by 2500 mL /min. Renal blood flow (normal 800 mL ) increases by 400 mL /min. The blood flow through the skin and mucous membranes reaches a maximum of 500 mL /min by 36th week. Heat sensation, sweating or stuffy nose complained by the pregnant women can be explained by the increased blood flow .

69. METABOLIC CHANGES

70. METABOLIC CHANGES GENERAL METABOLIC CHANGES PROTEIN METABOLISM CARBOHYDRATE METABOLISM FAT METABOLISM LIPID METABOLISM IRON METABOLISM

71. GENERAL METABOLIC CHANGES Total metabolism is increased due to the needs of the growing fetus and the uterus. Basal metabolic rate is increased to the extent of 30% higher than that of the average for the nonpregnant women.

72. PROTEIN METABOLISM There is a positive nitrogenous balance throughout pregnancy . At term, the fetus and the placenta contain about 500 gm of protein and the maternal gain is also about 500 gm chiefly distributed in the uterus, breasts and the maternal blood. Amino acids are actively transported across the placenta to the fetus .

73. CARBOHYDRATE METABOLISM Transfer of increased amount of glucose from mother to the fetus is needed throughout pregnancy. Insulin secretion is increased. Plasma insulin level is increased due to a number of contrainsulin factors.

74. Increased insulin level favors lipogenesis (fat storage). During maternal fasting, there is hypoglycemia , hypoinsulinemia , hyperlipidemia and hyperketonemia . Lipolysis generates fatty acids for gluconeogenesis and fuel supply. Plasma glucagon level remains unchanged .

75. FAT METABOLISM An average of 3–4 kg of fat is stored during pregnancy mostly in the abdominal wall , breasts , hips and thighs . Plasma lipids and lipoproteins increase appreciably during the later half of pregnancy due to increased estrogen , progesterone, hPL and leptin levels.

76. LIPID METABOLISM HDL level increases by 15%. LDL is utilized for placental steroid synthesis.

77. IRON METABOLISM Iron is absorbed in ferrous form duodenum and jejunum and is released into the circulation as transferrin. About 10% of ingested iron is absorbed. Iron is transported actively across the placenta to the fetus . Total iron requirement during pregnancy is estimated approximately 1000 mg.

78. In the absence of iron supplementation, there is drop in hemoglobin , serum iron and serum ferritin concentration at term pregnancy Thus pregnancy is an inevitable iron deficiency state.

79. SYSTEMIC CHANGES

80. SYSTEMIC SYSTEM RESPIRATORY SYSTEM Acid base balance The pH rises URINARY SYSTEM Kidney Ureter Bladder ALIMENTARY SYSTEM LIVER AND GALLBLADDER NERVOUS SYSTEM CALCIUM METABOLISM AND LOCOMOTOR SYSTEM

81. RESPIRATORY SYSTEM There is elevation of the diaphragm by 4 cm . Total lung capacity is reduced by 5% due to this elevation. Total pulmonary resistance is reduced due to progesterone effect. The subcostal angle increases from 68° to 103°, the transverse diameter of the chest expands by 2 cm and the chest circumference increases by 5–7 cm . A state of hyperventilation occurs during pregnancy leading to increase in tidal volume.

82. Acid base balance The hyperventilation causes changes in the acid base balance. The arterial PaCO2 falls from 38–32 mm Hg and PaO2 rises from 95–105 mm Hg. These facilitate transfer of CO2 from the fetus to the mother and O2 from the mother to the fetus .

83. The pH rises The pH rises in order of 0.02 unit and there is a base excess of 2 mEq /L . Thus, pregnancy is in a state of respiratory alkalosis. Maternal O2 consumption is increased by 20–40% due to increased demand of the fetus , placenta and maternal tissues.

84. URINARY SYSTEM Kidney There is dilatation of the ureter, renal pelvis and the calyces. The kidneys enlarge in length by 1 cm . Renal plasma flow is increased by 50–75%. Glomerular filtration rate (GFR) is increased by 50%. Increased GFR causes reduction in maternal plasma levels of creatinine , blood urea nitrogen (BUN) and uric acid.

85. Ureter : Ureters become atonic due to high progesterone level. Dilatation of the ureter above the pelvic brim with stasis is marked on the right side specially in primigravidae . It is due to dextrorotation . The stasis is marked between 20–24 weeks.

86. Bladder: There is hyper-trophy of the muscles and elastic tissues of the wall. In late pregnancy, the bladder mucosa becomes edematous due to venous and lymphatic obstruction especially in primigravidae following early engagement. Increased frequency of micturition is noticed at 6–8 weeks of pregnancy which subsides after 12 weeks. Stress incontinence may be observed in late pregnancy due to urethral sphincter weakness.

87. ALIMENTARY SYSTEM The gums become conge- sted and spongy and may bleed to touch. Muscle tone and motility are diminished. Cardiac sphincter is relaxed and regurgitation of acid gastric content into the esophagus ( chemical esophagitis and heart burn). Diminished gastric secretion and delayed emptying time of the stomach. Atonicity of the gut leads to constipation .

88. LIVER AND GALLBLADDER No histological change in the liver cells, but the functions are depressed. There is mild cholestasis ( estrogen effect). Marked atonicity of the gallbladder (progesterone effect)

89. NERVOUS SYSTEM Temperamental changes are found during pregnancy and in the puerperium . Nausea, vomiting, mental irritability and sleeplessness are probably due to some psychological background. Postpartum blues , depression or psychosis may develop in a susceptible individual.

90. NERVOUS SYSTEM Carpal tunnel syndrome may appear in the later months of pregnancy. Similarly paresthesia and sensory loss over the anterolateral aspect of the thigh may occur. It is due to compression of the lateral cutaneous nerve of the thigh.

91. CALCIUM METABOLISM AND LOCOMOTOR SYSTEM There is increase in the demand of calcium by the growing fetus to the extent of 28 g, 80% of which is required in the last trimester. Daily requirement of calcium during pregnancy and lactation averages 1–1.5 g. Maternal total calcium levels fall but serum ionized calcium level is unchanged.

92. There is increased mobility of the pelvic joints due to softening of the ligaments caused mainly by hormone . This along with increased lumbar lordosis during later months of pregnancy due to enlarged uterus produces backache and waddling gait .

93. Thank You