physiologicalchangesduringpregnancy-120719105010-phpapp02.pdf
- 1. Physiological changes during pregnancy Dr Nailla Memon Senior Registrar SZWH Larkana
- 2. Genital changes • The body of the uterus - Height and weight (hyperplasia) the height increases from 7.5 cm to 35cm the weight increases from 50g to 1000g at term - Uterine ligaments show hypertrophy - Dextro-rotation the uterus is tilted and twisted to the right in 80% of cases - Lower uterine segment (LUS) the LUS is formed from the isthmus formed from the 4th month to reach 10 cm at full term
- 3. Genital changes • The cervix - edema and congestion, and becomes soft - mucus plug (operculum): cervical mucus closing the cervical canal - increased secretion from its glands • The vulva shows increased vascularity and varicosities
- 4. Genital changes • The vagina - shows increased vascularity soft, moist and bluish - distention of vagina at birth • The ovary shows increased vascularity and size one ovary contains the corpus luteum • Pelvic ligaments - relaxation of the ligaments - relaxation of the pelvic joints - the pelvis become more mobile and increases in capacity
- 5. Breast changes • Increased size and vascularity warm, tense and tender • Increased pigmentation of the nipple and areola • Secondary areola appear (light pigmentation around the 1ry areola) • Montgomery tubercules appear on the areola (dilated sebaceous glands) • Colostrum like fluid is expressed at the end of the 3rd month
- 6. Skin changes • Pigmentation due to increased melanocyte stimulating hormone: - linea nigra: pigmentation of the linea alba, more marked below the umbilicus - chloasma gravidarum: Butterfly pigmentation of the face (mask of pregnancy) • Striae gravidarum - stretch of the abdominal wall rupture of the subcutaneous elastic fibers pink lines in flanks - become white after labor
- 7. Weight increase • There is an increase weight of approximately 12.5 Kg at term • The main increase occurs in the 2nd half of the pregnancy, 0.5 Kg/week • Causes: growth of the conceptus enlargement of the maternal organs maternal storage of fat increase in maternal blood and interstitial fluid
- 8. Skeletal changes • Increased lumbar lordosis • Relaxation of pelvic joints and ligaments due to progesterone and relaxin
- 9. Urinary changes • Kidneys - increase in size - hydronephrosis - effective renal plasma flow is increased • Dilatation of the ureters - Atony of the ureteric muscles caused by progesterone and relaxin hydro-ureter - vesico-ureteric reflux increased - pressure of the uterus on the ureter affects more the right ureter due to the dextro-rotation of the uterus Changes in the ureter in pregnancy leads to urinary stasis and pyelitis
- 10. Urinary changes • Frequency of micturation causes: 1st trimester: pressure of the uterus on the bladder late in pregnancy: engagement of the head • Urinary output - diminished on a normal fluid intake - increase in tubular reabsorption - 100 extra liters of fluid pass into the renal tubules each day - extracellular water is increased by 6 to 7 liters during pregnancy - this is due to increased amounts of aldosterone progesterone and oestrogen
- 11. Gastro-intestinal changes • Increased salivation (ptyalism) • Taste is often altered very early in pregnancy • Increase appetite & thirst frequent small snacks • Heart burn (reflux oesophagitis) relaxation of the cardiac sphincter due to progesterone and relaxin • Emesis gravidarum, morning sickness in 50 % • Decreased gastric acidity, which interfere with iron absorption • Constipation reduced gut motility due to progesterone increased water and salt absorption
- 12. Gastro-intestinal changes • Liver - Hepatic synthesis of albumin, plasma globulin and fibrinogen increases - Total hepatic synthesis of globulin increases stimulated by estrogen - Hormone-binding globulins rise - gall bladder increases in size and empties more slowly - relaxation of gall bladder increases the tendency of stone formation - cholestasis is almost physiological - secretion of bile is unchanged
- 13. Cardiovascular changes • Fall in total peripheral resistance by 6 weeks gestation to a nadir ~ 40% by mid gestation • Circulatory underfilling activation of renin-angiotensin- aldosterone system necessary expansion of the plasma volume the bigger the expansion, the bigger the baby birthweight • Total extracellular volume 16% by term • Plasma osmolality by 10mOsm/Kg as water is retained
- 14. Cardiovascular changes • The heart - the heart rate rises synchronously by 10-15 b.p.m. from 70 to 85 b.p.m. - stroke volume rises - cardiac output begins to rise by 35-40% in a first pregnancy and ~ 50% in later pregnancies
- 15. Cardiovascular changes • The blood pressure - Korotkoff 5 used with auscultatory techniques - slight drop in the 2nd trimester small fall in systolic, greater fall in diastolic B.P. opening of arterio-venous shunts at the placenta increased pulse pressure - supine hypotension syndrome in 8% of the women 2nd half of the pregnancy: maternal hypotension occurs in the supine position due to pressure of the uterus on the inferior vena cava decreased venous return and cardiac output
- 16. Cardiovascular changes • Noradrenaline - pressor response to angiotensin II reduced in normal pregnancy, unchanged to noradrenaline - plasma noradrenaline is not increased in normal pregnancy • Pulmonary circulation - able to absorb high rate of flow without an increase in pressure - pressure in right ventricle, pulmonary arteries and capillaries does not change - pulmonary resistance falls in early pregnancy - progressive venodilatation + rises in venous distensibility + capacitance throughout a normal pregnancy
- 17. Respiratory changes • Tidal volume rises by 30% in early pregnancy 40-50% by term • Fall in expiratory reserve and residual volume decrease the threshold increase the sensitivity of medulla oblongata to CO2 • Respiratory rate does not change the minute ventilation rises by a similar amount from 7.25L to 10.5L • Elevation of the diaphragm in late pregnancy dyspnea Driven by progesterone
- 18. Respiratory changes • Carbon dioxide production rises sharply during the 3rd trimester as fetal metabolism increases • The fall in maternal P CO2 - allows more efficient placental transfer of CO2 from the fetus - results in a fall in plasma bicarbonate concentration ( from 24-28 mmol/L to 18-22 mmol/L) fall in plasma osmolality venous pH rises slightly ( from 7.35 to 7.38)
- 19. Respiratory changes • The increased alveolar ventilation small rise in PCO2 (from 96.7 to 101.8 mmHg) • Rightward shift of the maternal oxyhaemoglobin dissociation curve ( due to an increase in 2,3-DPG in erythrocytes) oxygen unloading to the fetus which has: - lower PCO2 (25-30 mmHg, 3.3-4 KPa) - marked leftward shift of the oxyhaemoglobin dissociation curve, (due to lower sensitivity of fetal haemoglobin to 2,3-DPG)
- 20. Respiratory changes • Increase of 16% in oxygen consumption by term • Fall in arterio-venous oxygen difference • Pregnancy places greater demands on the cardiovascular than the respiratory system
- 21. Haematological changes • Circulating red cell mass increases by 20-30% ( rises more in multiple pregnancies and iron supplement) • Serum iron concentration falls absorption from gut and iron-binding capacity rise • Plasma folate concentration halves by term ( renal clearance) red cell folate concentration falls less • Mild maternal anaemia associated with increased placental/birthweight ratio decreased birthweight
- 22. Haematological changes • Erythropoietin rises especially if iron supplement not taken • Human placental lactogen may stimulate haematopoiesis • Fall in packed cell volume from 36% in early pregnancy to 32% in the 3rd trimester ( normal plasma volume expansion) • WBC count rises ( increase in polymorphonuclear leucocytes) • Neutrophil number rises with oestrogen peak at 33 weeks stabilizing after that until labour and the puerperium, when they rise sharply
- 23. Haematological changes • T and B lymphocyte counts do not change but their function is suppressed ( women become more susceptible to viral infections, malaria and leprosy) • Platelet count and platelet volume are largely unchanged
- 24. Haematological changes • Coagulation - factors VII, VIII and X rise - absolute plasma fibrinogen doubles - antithrombin III falls - erythrocyte sedimentation rates increase - Protein C unchanged - Protein S concentrations, co-factor of protein C, fall in 1st & 2nd trimesters - plasma fibrinolytic activity decreases during pregnancy & labour returns to normal values within an hour of delivery of placenta
- 26. Endocrinal changes • Pituitary - anterior pituitary increases in size and activity - posterior pituitary releases oxytocin on the onset of labor • Thyroid - increases in size and activity: physiological goiter - most pregnant women are euthyroid - thyroid binding globulin concentrations double (not other thyroid binding proteins) - total T3, T4 are increased (not the free T3 ,T4) • Parathyroid increases in size and activity to regulate calcium metabolism
- 27. Endocrinal changes • Adrenals - increases in size and activity - total cortisol is increased (free cortisol unchanged) • Placental hormones Progesterone - produced by the corpus luteum - levels rise steadily during pregnancy, output reaches 250mg/day - actions: colon activity reduced, nausea, constipation reduced bladder and ureteric tone diastolic pressure reduced, venous dilatation raises temperature
- 28. Endocrinal changes • Placental hormones Oestrogens - source: ovary in early pregnancy later, oestrone and oestradiol produced by the placenta increased a hundredfold oestriol produced by the placenta and fetal adrenals increased thousandfold - levels: output of oestrogens reaches a maximum of at least 30-40mg/day oestriol accounts 85% levels increase up to term
- 29. Endocrinal changes • Placental hormones Oestrogens - possible actions: 1- induce growth of uterus and control its function 2- responsible for the development of breasts ( with progesterone) 3- alter chemical constitution of connective tissue, become more pliable 4- cause water retention 5- reduce sodium excretion
- 31. Metabolic changes • Carbohydrate metabolism - pregnancy is hyperlipidaemic and glucosuric - after mid-pregnancy, resistance of insulin develops - plasma glucose concentrations rise, maintained between 4.5-5.5 mmol/L - glucose crosses the placenta, the fetus uses glucose as primary energy substrate, transport occurs by carrier mediated mechanism - the insulin resistance is endocrine-driven, via increase in cortisol and hPL - concentrations of glucagons and the catecholamines are unaltered
- 32. Metabolic changes • Carbohydrate metabolism - carbohydrate deposited in the liver as glycogen - some escapes to general circulation - portion metabolised by the tissues: converted to depot fat stored as muscle glycogen - first noticeable change occurs in blood sugar - tested by giving a load of oral glucose (glucose tolerance test) - the blood sugar, after meal, remains high facilitating placental transfer
- 33. Metabolic changes • Carbohydrate metabolism - with increased placental production of steroid, less glycogen deposited in liver and muscles - the effect of fasting is pronounced in pregnancy overnight fast of 12hrs hypoglycaemia, production of ketone bodies
- 34. Metabolic changes • Protein metabolism - positive nitrogen balance - on average 500 g of protein retained by the end of pregnancy - blood and urine urea are reduced • Fat metabolism - by 30 weeks, 4Kg are stored in form of depot fat in the abdominal wall, back and thights modest amount in breasts