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Physiological Changes During Pregnancy

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Presentation on theme: "Physiological Changes During Pregnancy"— Presentation transcript:

1 Physiological Changes During Pregnancy
There are many physiologic changes in pregnancy. Some mimic the signs, symptoms, or laboratory finding of disease in the nonpregnant woman yet are normal in pregnancy. Therefore , knowledge of normal maternal physiologic changes helps avoid unnecessary diagnostic or therapeutic interventions.

2 The normal adaptations that a woman undergoes during pregnancy to better accommodate the embryo or fetus. They are physiological changes, that is, they are entirely normal, and include cardiovascular hematologic metabolic renal respiratory

3 To provide a suitable environment for the nutrition growth and development of the fetus and to prepare the mother for the process of parturition and subsequent support for the newborn infant

4 Hormonal changes Estrogen is mainly produced by the placenta and is associated with fetal well–being. Women also experience increased human chorionic gonadotropin (β-hCG); which is produced by the placenta. This maintains progesterone production by the corpus luteum. The increased progesterone production, first by corpus luteum and later by the placenta, functions to relax smooth muscle. Elevated progesterone levels also contribute to an increase in minute ventilation to 50% greater than non-pregnant levels.

5 Hormonal changes Prolactin levels increase due to maternal pituitary gland enlargement by 50%. This mediates a change in the structure of the mammary gland from ductal to lobular-alveolar. Parathyroid hormone is increased which leads to increases of calcium uptake in the gut and reabsorption by the kidney. Adrenal hormones such as cortisol and aldosterone also increase. Human placental lactogen (hPL) is produced by the placenta and stimulates lipolysis and fatty acid metabolism by the woman, conserving blood glucose for use by the fetus. It can also decrease maternal tissue sensitivity to insulin, resulting in gestational diabetes.

6 Hormonal changes

7 Hormonal changes Thyroid enlargment High level T3,T4 Normal TSH
Subclinical hypothyrodism

8 Cardiovascular changes
Position and size of heart ECG changes Increased heart rate (+15%) 15-degree left axis deviation Inverted T-waves in lead III Q in lead III and AVF Unspecific ST changes 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 to the left. With the anatomical changes in the heart, there may also be alterations in heart rhythm and electrocardiographic finding, and non pathologic murmurs may occur. ECG changes are probably due to the change in position of the heart and may include a degree shift to the left in the electrical axis. There may be reversible ST, T and Q waves changes. In order to detect pathologic changes in the ECG, one has to know about physiologic changes during pregnancy. Diaphragmatic elevation causes leftward deviation of the heart. The result is a 15 degree left axis deviation. Q wave may be present in leads III and AVF. Inverted T waves may be seen in lead III. Unspecific ST changes may occur. Caused by the leftward deviation, the heart may appear enlarged in the chest roentgenogram.

9 Cardiovascular changes
Appear larger

10 Cardiovascular changes
Heart rhythms and murmurs: soft , transient Caution: How to interpret these murmurs Inferior vena cava syndrome: In the supine position, the inferior vena cava is compressed by the enlarged uterus, resulting in decreased cardiac output. Some women may have symptoms that include dizziness, light-headedness, and syncope. The first heart sound may be split, with increased loudness of both portions. As many as 90% gravid women may have a late systolic or ejection murmur attributable to the increase in the stroke volume and the decrease in blood viscosity. The murmur disappear soon after birth. Caution is needed in interpreting murmurs during pregnancy, particularly systolic murmurs, because such physiologic alterations do not necessarily indicate heart disease and must be differentiated from pathologic changes. During pregnancy, cardiac output is very sensitive to positional alterations. In the supine position, the inferior vena cava is compressed by the enlarged uterus, resulting in decreased cardiac output. Although most women do not become overtly hypotensive when lying supine, some may have symptoms that include dizziness, light-headedness, and syncope. This is termed the inferior vena cava syndrome.

11 Cardiovascular changes
blood volume slowly increases by 40-50%. The increase is mainly due to an increase in plasma volume through increased aldosterone. It results in an increase in heart rate (15 beats/min more than usual), stroke volume, and cardiac output. Cardiac output increases by about 50%, mostly during the first trimester. The systemic vascular resistance also slightly decreases due to smooth muscle relaxation and overall vasodilation caused by elevated progesterone. Diastolic blood pressure consequently decreases If the blood pressure becomes abnormally high, the woman should be investigated for pre-eclampsia and other causes of hypertension.

12 Cardiovascular changes
Stroke volume % Heart rate % Cardiac output % Oxygen consumption % SVR (systemic vascular resistance) -5% Systolic BP mmHg Diastolic BP mmHg Mean BP mmHg Increases in stoke volume and heart rate are responsible for the changes in cardiac output. Increased metabolic demands of mother and fetus are the cause for this rise in cardiac output. The resting oxygen consumption of the parturient increases approximately 20% compared to non-pregnant levels. Increased hormonal levels, estrogen and prostaglandins cause a vasodilatation and therefore a decrease in systemic vascular resistance and pulmonary vascular resistance. Decreased peripheral resistance causes a small decrease in systolic blood pressure and a more marked decrease in diastolic blood pressure.

13 Cardiovascular changes
Blood volume % Plasma volume % Red blood cell volume % Dilutional anemia Increase cardiac output Vasodilatation Maternal blood volume increases during pregnancy, reaching a maximum of 30% at approximately weeks of gestation. Plasma volume increases from ml/kg which represents a rise of 40%. The different rate of increase in blood and plasma volume accounts for the relative anemia of pregnancy. The dilutional anemia of the parturient decreases the oxygen carrying capacity of the blood. Several mechanism compensate for this disadvantage: increased cardiac output, decreased blood viscosity, vasodilatation and right shift of the oxyhemoglobin dissociation curve provide increased flow and better oxygen extraction in the tissue. Cardiac out put begins a progressive rise in the first trimester and peaks by weeks of gestation. The rise represents the increased metabolic demands of the mother and fetus as pregnacy progresses.

14 Hematologic system Blood volume +40% Dilutional anemia Hb 110 g/L
Leukocytosis ,000/ml Platelet not change Sedimentation rate increase, 100m/h Hypovolemia begins in the first trimester, increases rapidly in the second trimester and plateaus at about the 30th week. The total blood leukocyte count increases during normal pregnancy from a prepregnancy level of /ul to /ul in the last trimester. The cause of the rise in the leukocyte count , which primarily involves the polymorphonuclear , has not been established, although it seems likely to be caused by increased demargination of white cells. the increase starts from 7-8 weeks of gestation and peaked at 30 weeks. Some studies have reported an apparent increase in the production of platelets (thrombocytopoiesis) during pregnancy that is accompanied by progressive platelet consumption.

15 Hematologic system Clotting factors: hypercoagulable, throboembolism
Fibrinogen (factor I) % (4.5 vs 3 g/L) Factor VIII increase Factors VII, IX, X and XII increase Prothrombin time, PT shortened activated partial thromoplastin time shortened Fibrinolytic activity decrease Pregnancy is considered a hypercoagulable state with an increased risk of venous thromboembolism both during pregnancy and the puerperium. The fibrinolytic activity is depressed. The risk of thromboembolism is approximately 2 times normal during pregnancy and increases to 5.5 times normal during the puerperium. Understanding these physiologic changes is necessary to manage two of the more serious problems of pregnancy, hemorrhage and thromoembolic disorder, both caused by disorders in the mechanism of hemostasis.

16 Hematologic system Iron : active transplacental transfer
Requirement mg increase maternal red cell mass mg fetal development mg compensate for normal iron loss mg To supply, 300 mg of ferrous sulfate is needed, and twice the dose for anemic patients.

17 Pulmonary changes Mucosal hyperemia Subcostal angle
Chest circumference and diameter Tidal volume % PO2 is increased, PCO2 is decreased. Total lung capacity decrease % Minute ventilation % Mild respiratory alkalosis Pregnancy related changes of the respiratory system are the result of both anatomic and functional changes.

18 Gastrointestinal change
Morning sickness hyperremesis gravidarum (weight loss, ketonemia and electrolyte imbalance) Dietary craving: pica Decreased gastrointestinal motility: reflux and heartburn Gallbladder function, cholestasis Hyperemia and softening of the gums (epulis) Hemorrhoid Appendix displaced The exact etiology of this nausea is unknown, the morning sickness appears related to elevated levels of pregesterone, human chorionic gonadotropin, and relaxation of the smooth muscle of the stomach. In general, there is decreased gastrointestinal motility during pregnancy because of increasing levels of progesterone. As a result, gastric emptying time is prolonged and there is decreased eophageal tone and imcompetence of the esophageal tone and incompetence of the esophageal-stomach sphincter, leading to gastric reflux and heart burn, common complaints in pregnancy.

19 Renal changes Kidney slightly enlarged Renal plasma flow +35%
Glomerular filtration rate % Serum creatinine, uric acid urea and nitrogen Renin, angiotensin I and II Renin substrate Glucosuria (50%) + Normal pregnant patients are relatively resistant to the hypertensive effects of the increased levels of renin-angiotensin-aldosterone, whereas patients with hypertensive disease of pregnancy are not. Glucosuria during pregnancy is not necessarily abnormal. Glucose is excreted in the urine at some point during pregnancy in more than 50% of women. Glucosuria may be explained by the increase in GFR with impairment of tubular resorption capacity for filtered glucose. Glucosuria can also predispose pregnant women to urinary tract infection.

20 Renal changes renal pelvis dilated Ureters (esp. right side) dilated
Bladder tone reduced Bladder capacity reduced Residual volume increased Chance of pyelonephritis increaased Increased residual volume and with the dilated collecting system, urinary stasis results, predispose to an increased incidence of pyelonephritis in patients with asymptomatic bacteriuria.

21 Breasts Engorgement and venous prominence
Mastodynia (breast ternderness): tingling to frank pain caused by hormonal responses of the mammary ducts and alveolar system Montgomery’s tubercles: enlargement of circumlacteal sebaceous glands of the areola Colostrum secretion Circulatory increases result in breast engorgement and venous prominence. Similar tenderness may occur just before menses. Montgomery’s tubercles: sometimes called montgomery’s follicles, the small elevations surrounding the areolae, enlarge and become more prominent. enlargement of these glands occurs at 6-8 weeks and is due to hormonal stimulation. Colostrum: during the latter portion of pregnancy, a thick yellow fluid can be expressed from the nipples. Ultimately, lactation depends on synergistic actions of estrogen, progesterone, prolactin, hPL , cortisol and insulin.

22 Skin changes Vascular spiders Striae gravidarum
Hyperpigmentation (estrogen and melanocyte-stimulating hormone) Linea alba——linea nigra Chloasma ( Face Mask) Skin nevi

23 Reproductive tract Uterus: from 50g - 1100g from < 10ml – 5L
<2% % of cardiac output Isthmus uteri —— lower segment of the uterus The uterus undegoes an enormous increase in weight from the 70g nonpregnant size to approximately 1100g at term, primarily through hypertrophy of existing myometrial cells. Also, the uterine cavity, which in the nongravid state has a volume of less than 10 ml, increases up to as much as 5 liters. Cardiac output to the uterus is less than 2% in the nongravid state, but increases to 15%-20% at term.

24 Reproductive tract Braxton Hicks contraction: sporadic, irregular, asymmetrical, and painless, low pressure, lasting < 30 sec

25 Characteristics of True and False Labor
Regular Contractions Stronger, longer, closer together Bloody show often present Cervix effaced and dilated Head is fixed between contractions Sedation does not stop true labor Irregular No change in contraction characteristics No show No cervical change Head may be ballotable Sedation stops false labor

26 Reproductive tract Cervix and vulva , Chadwick’s sign
congestion of the pelvic vasculature, cause bluish or purplish discoloration of the cervix and vulva Leukorrhea: increase in vaginal discharge, rich in glucose, lactic acid, low vaginal pH Ovary: slightly enlarged, corpus luteum regresses after weeks’ gestation The increase of vaginal discharge consists of epithelial cells and cervical mucus due to hormonal stimulation. Cervical mucus that has been spread on a glass slide and allowed to dry no longer forms a fernlike pattern but has a granular appearance.

27 Metabolism Basal metabolism rate, BMR +15-20% Weight gain 12.5kg
Fetus g Placenta g Amniotic g Uterus g Plasma, red cells g Mammary glands g Extracellular, extravascular water g Deposition of fat and protein g Insulin resistance

28 Musculoskeletal a woman's foot can grow by a half size or more during pregnancy, the increased body weight of pregnancy, fluid retention, and weight gain lowers the arches of the foot, further adding to the foot's length and width. The influences of increased hormones such as estrogen and relaxin initiate the remodeling of soft tissues, cartilage and ligaments. Certain skeletal joints such as the pubic symphysis and sacroiliac widen or have increased laxity.

29 Lumbar lordosis

30 Immune system the immune system significantly changes during pregnancy and these changes are essential for normal placentation and maintenance of a healthy pregnancy pregnant women are more sensitive to certain infections This raises questions on the safety of vaccination during pregnancy

31 placenta & fetal circulation

32 Anatomy And Physiology
- Fetus depends on placenta to meet O2 needs while organs continue formation -oxygenated blood flows from the placenta to the fetus via the umbilical vein After reaching fetus the blood flows through the inferior vena cava

33 The Placenta - The circulatory system of the mother is not directly connected to that of the fetus, so the placenta functions as the respiratory center for the fetus - As well as a site of filtration for plasma nutrients and wastes. Water, glucose, amino acids, vitamins, and inorganic salts freely diffuse across the placenta along with oxygen. - The uterine arteries carry oxygenated blood to the placenta, and permeates the sponge like material there.

34 Fetal Circulation : - Facilitates gas and nutrient exchange between maternal and fetal blood. Umbilical cord 2 umbilical arteries: Return non-oxygenated blood, fecal waste, CO2 to placenta 1umbilical vein : brings oxygenated blood and nutrients to the fetus

35 How does the blood move?? - Umbilical vein carries oxygenated blood and nutrients from the placenta to the fetus. How is the blood dispersed?? - ½ Of the blood enters the liver while the other half comes into the ductus venosus and then into the inferior vena cava

36 Foramen Ovale - Blood is shunted from right atrium to left atrium, skipping the lungs. - More than one-third of blood takes this route. - a valve with two flaps that prevent back-flow.

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39 What is happening further down??
Common iliac arteries branch into the external and internal iliacs. The blood in the internal iliacs come into the umbilical arteries and flow back to the placenta to gather oxygen and to get rid of the waste products Some of the blood moves from the aorta through the internal iliac arteries to the umbilical arteries, and re-enters the placenta, the maternal circulation

40 FETAL CIRCULATION - Low pressure system - Lungs are closed - Most oxygenated blood flows between the atria of the heart through the foramen ovale - This oxygen rich blood flows to the brain through the ductus arteriosus

41 What happens after birth
What happens after birth? Once the baby is born and the lung, renal, digestive and liver functions are working the fetal circulation undergoes some changes since they are no longer needed

42 Conversion Of Fetal To Infant Circulation
At birth - Clamping the cord shuts down low-pressure system - Increased atmospheric pressure(increased systemic vascular resistance) causes - Lungs to inflate with oxygen - Lungs now become a low-pressure system - Pressure from increased blood flow

43 Conversion (cont) What happens to these special structures after birth? Umbilical arteries atrophy Umbilical vein becomes part of the fibrous support ligament for the liver The foramen ovale, ductus arteriosus, ductus venosus atrophy and become fibrous ligaments

44 Overview Of Conversion - Umbilical cord is clamped - Loose placenta - Closure of ductus venosus ductus arteriosus,foramen ovale - Blood is transported to liver and portal system

45 Fetal vs. Infant Circulation
- Low pressure system - Right to left shunting - Lungs non-functional - Increased pulmonary resistance - Decreased systemic resistance - High pressure system Left to right blood flow Lungs functional Decreased pulmonary resistance Increased systemic resistance

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48 A 25 year old patient presents with a 4 cm ovarian cyst on exam, she is 10 weeks pregnant, Management may includes Laparoscopy laparotomy Reassurance, and repeat scan in 3-4 weeks Cancer screening

49 In a normal singleton pregnancy, maternal blood volume
increases by 10-15% increases by 45% decreases by 10-15% decreases by 45%

50 Which of the following is not characteristic of a normal pregnancy?
A. cardiac volume increases by 10% B. the rest pulse rate increases by approximately 10-15% beats per min C. arterial blood pressure and vascular resistance increases D. The heart is displaced upward and to the left

51 A pregnant lady was told by her physician that she has Epulis, which is a pregnancy-related vascular swelling of the: A. Gums B. Nail bed C. Larynx D. Nares


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