Physiology: Maternal Impact of Pregnancy During Gestation - Essay Example

? MATERNAL IMPACT OF PREGNANCY (DURING GESTATION) by of the of the of the School 3 October, 2013 Table of Contents Table of Contents 1 Mattison, D R 2013, Clinical Pharmacology during Pregnancy, Elsevier Inc., London. 15 Symonds, ME and Ramsay, MR 2010, Maternal-Foetal Nutrition during Pregnancy and Lactation, Cambridge University Press, Cambridge. 15 OUTLINE 1. INTRODUCTION 2. PHYSIOLOGY OF NORMAL PREGNANCY a. Prenatal development b. Uterine changes c. Placental development and function 3. STRUCTURAL AND FUNCTIONAL CHANGES TO THE MATERNAL SYSTEM a. Musculoskeletal system b. Gastrointestinal system 4. MATERNAL PHYSIOLOGY ADAPTATION OF THE CARDIOVASCULAR SYSTEM a. Physical changes b. Haemodynamic changes c. Changes in maternal coagulation and haemostasis 5. MATERNAL PHYSIOLOGICAL ADAPTATION OF THE RESPIRATORY SYSTEM a. Lung volume/function related changes b. Acid/base changes c. Changes in respiratory function in relation to mechanical, hormonal and foetal change 6. MATERNAL PHYSIOLOGICAL ADAPTATION OF THE RENAL SYSTEM a. Structural changes b. Changes in renal haemodynamics c. Fluid and electrolyte homestasis 7. SUMMARY 1.0 Introduction The female reproductive system undergoes changes right from birth to the delivery of the infants. As the foetus begins to develop, the female body gradually changes with time, in order to accommodate it. Poor heath before pregnancy and maternal complications can cause devastating effects on the pregnancy or maternal health, in case they turn out severe. A pregnant woman is normally expected to carry the pregnancy for nine months before delivery. However, certain complications arising from accidents or health conditions may force her into early delivery. Along the gestation period, she may be confronted with situations that demand her adaptation to fit her body system needs in behaviour, health wise, psychologically, and physically, to protect her pregnancy and health. After a sperms penetration into the ovum and the two nuclei fuses, biological processes occur to develop a foetus. A pregnant woman is supposed to take precautions and monitor her health and the changes taking place in her body. This is because the pregnancy may affect some parts of the body system such as the renal system, cardiovascular system, respiratory functioning among others. 2.0 Physiology of Normal Pregnancy 2.1 Prenatal development Normally, after the zygote is formed, its transforms through a series of changes before it forms into a ready baby for delivery. This development is split into 3stages; germinal, embryonic and foetal. The germinal stage occurs within the first 2 weeks (from inception to implantation) and is characterized by cell divisions, where the zygote continuously replicates itself into multiple cell organisms (blastocysts) with similar genetic material (Pastorino & Doyle-Portillo 2006). As the cells divide, they move down the fallopian tube to the uterus, but remain wandering around for some days, which is then followed by their implantation on the uterus. All this time, the cells receive nourishment from the yolk of the egg cell until they implant on the uterus to acquire it externally. The blastocysts are essential cells that tend to group themselves for the formation of various structures. Their outer and inner membranes play a critical role in development of the embryo, its structures, and blood vessels. The embryonic stage starts from the 2nd to the 8th week; it’s a precarious moment of prenatal development, which involves major organ differentiation (like skin, bones etc) and body system formation (the cardiovascular, respiratory digestive etc) (Pastorino & Doyle-Portillo 2006). The organs of the embryo are usually very small; therefore, they are nourished through the placenta from the maternal blood vessels on the uterine wall to the umbilical code that connects to it. With continued supply of nutrients to the embryo, its structures, organs, and systems enhance and function properly. From the 9th week, the foetus continues to grow and mature in size and weight all the way till ready for birth (Pastorino & Doyle-Portillo 2006). Its fully formed organs can be distinguished visually within the first 4 to 5 months and by the time the foetus is 6 months, they can respond physically by movements with the organs capable of sustaining independent life. 2.2 Uterine changes The growth of a normal pregnancy demands internal maternal changes of a woman’s reproductive system and hormonal releases. The genital organs, cervix, uterus, ovaries and the hormones functional in reproduction are involved in the changes to accommodate the developing foetus. Uterine muscle fibres experience hypertrophy and hyperplasia, the cervix softens, uterine blood flow increases, and mammary glands enlarge (Padubidri & Anand 2006). 2.3 Placental development and function The blastocysts outer membrane named trophoblast is the placenta’s forerunner. Its inner layer (cytotrophoblast) cells continuously proliferate and differentiate throughout gestation, resulting to formation of extravillous trophoblast. It follows that the cytotrophoblast remodels the spiral arteries when they move into the maternal decidualized endometrium, to enable enhanced oxygen and nutrients supply to the placenta and the foetus (Forbes & Westwood 2010). The syncytiotrophoblast membrane increases in size to facilitate the transfer of the nutrients to the foetus as it grows. Hence with time, the placenta grows along the lining of the maternal uterus and the foetal villi grow into the uterine lining, such that the placenta will develop on the upper part of the uterus in normal cases. The waste products from the foetus are excreted through the placenta. 3.0 Structural and Functional Changes to the Maternal System 3.1 Musculoskeletal system The effects of increasing release of hormone relaxin, and continuous weight gain as the foetus develops cause the maternal musculoskeletal system changes. The pelvis of a woman tends to tilt forward causing the lumbosacrol and cervicodorsal regions to curve, due to the enlarging uterus. There is a relaxation of the sacrococcy-geal, sacroiliac and pelvic joints with the increased release of the sex hormone, the separation of the rectus muscles allowing the abdominal contents to protrude at the midline (Bruck 2008). The hormone facilitates the softening of the collagenous tissue and loosening up of the ligamentous. As the breasts enlarge, the shoulders also tend to pull forward. 3.2 Gastrointestinal system The digestive track changes in the gastrointestinal system influence the absorption of food. Enlargement of the uterus and upward growth in the pelvic cavity displaces adjacent maternal organs. The production of hormone progesterone minimizes the tone and mobility of smooth muscles to slow down the esophageal peristalsis. As a result, there is increased absorption of nutrients and water in the intestines. In the gastrointestinal system, the pressure of the lower esophageal sphincter decreases, whose effects can be increased regurgitation and heartburns (Datta, Kodali & Segal 2010). The stomach muscles also relax, and there is delayed gastric emptying, but as the pregnancy progresses, increase in gastric acid secretion causes reduced maternal gastric pH in the stomach. The volume of the stomach increases, which can cause frequent hunger. 4.0 Maternal Physiology Adaptation of the Cardiovascular System 4.1 Physical changes There are physical structural changes that occur along the heart region and some advances with the development of the foetus. The heart is displaced upward and towards the left due to the effects of pregnancy exertion on the ribcages and diaphragm (Gordon n.d.). The mass of the ventricular wall muscle increases as they thicken and as the vascular smooth muscle relax, vasodilatation occurs, which results to reduced resistance of the peripheral vascular. The heart rate increases in the months of gestation before its plateaus in the succeeding months once the foetal organs and system are (viable) fully formed to support independent life. 4.2 Haemodynamic changes From the 6th and 8th week of gestation to the 32nd week, there is 45% to at most 51% increase of blood volume, which is also accompanied by increased production of red blood cells, whose mass increases by 20-30 % at peak during pregnancy (Symonds & Ramsay 2010). However, the increase of the red blood cells is relatively slower, hence resulting to a decrease in hemoglobin concentration. That is why women have to take more iron to increase their red cell mass. In the blood, the content of sodium intake is high, but it becomes regulated later. The water intake is quite high to cater for the maternal needs as well as those of the foetus and its surrounding tissues and fluids. According to Chandra et al., platelets count does decrease, especially in the 3rd trimester, while the white blood cells increase in pregnancy (2012). Other hemodynamic changes are reduction in systemic blood pressure and an increase in cardiac output, whose effects are felt early in pregnancy and advances to their climax in the second trimester, then remains relatively stable towards delivery. 4.3 Changes in maternal coagulation and haemostasis Changes in the haemostatic profile are vital in the maintenance of the placenta function in pregnancy period. The decrease in platelets earlier mentioned are as a result of progressive destruction of platelets that lead to haemodilution. According to Prisco, Ciut and Falciani, during pregnancy, “the concentration of the coagulation factors VI, VIII, IX, X, XII and von Willebrand factor rises significantly,” with relative increase in plasma fibrinogen, and reduced plasma fibrinolytic activity (2005, p. 1-3). Increase of the estrogen hormones stimulates increased protein synthesis that in turn enhances the level of coagulation factors. 5.0 Maternal Physiological Adaptation of the Respiratory System 5.1 Lung volume/function related changes The enlarging uterus influences the lungs volume when it pushes the diaphragm and alters the chest wall configuration. The chest’s diameter of the maternal expands to cater for increased minute ventilation, but generally enables the total lungs volume to remain almost stable with very minimal reduction (Heidemann n.d.). The volume of the lungs reduces with the elevated movement of the diaphragm, hence reducing the total lung capacity by a small percentage, which heavily impacts on the functional residual capacity (FRC). During the pregnancy, the relation between the FRC and the inspiratory capacity tends to be inversely proportional. Meaning as the FRC is reduced by 20%, the inspiratory capacity increases to utmost 10% to recover from the increasing oxygen demand caused by FRC reduction (Gordon, n.d.). Increase in the tidal volume supports the increase in inspiratory capacity. 5.2 Acid/ base changes Hyperventilation in normal pregnancy is common; its occurrence however, exceeds increased metabolic requirements and causes a reduction in base excess, base buffer, and the plasma bicarbonate (Campbell & Klocke 2001). The body system compensates for respiratory alkalosis through the kidney excretion of the bicarbonate, but seeks to preserve a normal arterial PH by maintaining a lower serum bicarbonate level. Base line pH remains relatively normal ranging from 7. 39 to 7.42 (McCormack & Wise n.d.). 5.3 Changes in respiratory function in relation to mechanical, hormonal, and foetal change The mechanical pressure exerted by uterus accelerates changes in configuration of the thoracic cage. Enlarging uterus, exertion of diaphragm, and consequently the increasing abdominal pressure that reduces chest wall compliance causes serial changes in lung volume, especially the FRC as a consistent change in the static lung volume (McCormack & Wise n.d.). This follows a chest traverse diameter and chest circumference expansion of 2 and 5-7 centimetres respectively (Gordon n.d.). Two hormones; Estrogen and Progesterone increase with pregnancy, and influence anatomic changes and arterial partial pressure of oxygen respectively. High level of estrogen concentration stimulates secretion of mucous that may lead to nasal stuffiness or obstruction, while progesterone supports increased minute ventilation, which leads to PaCO2 decline and PaO2 incline for acid/base regulation (Mattison 2013). Progesterone also relaxes the muscle tissues to minimize airway resistance for proper inhalation and exhalation. 6.0 Maternal Physiological Adaptation of the Renal System 6.1 Structural changes The organs of the renal system show profound changes with relaxation and dilation of their smooth muscles. Maternal Kidneys enlarges by 1 to 1.5centimeters, and its volume increases mediated by the increase in volume of the renal vascular and intestinal system (Odutayo & Hladunewich 2012). The ureters and renal pelvic muscles are relaxed and dilated more profoundly on the right than the left, forcing the ureters to lengthen. Similarly, the bladder muscle relaxes and with the increased vascular tortuousity during mid pregnancy, anatomical changes of bladder elevation occur (Gordon n.d.). The relaxation of the bladder increases its capacity, but because of the uterus and foetus enlargement, its capacity is reduced, which fills fast and forces the mother to frequent urination. (American Medical Association n.d.) The diagram illustrates how uterus and foetal expansion compresses the bladder. 6.2 Changes in renal haemodynamics The renal vasodilatation arising from the anatomical and structural changes has a considerable effect on the RBF. Due to this there is increased blood volume combined with the high cardiac output, RBF increases. Although increase begins early in gestation, the rise in RBF can be to a high of 75 percent over that of non gravid level by the 16th week, and maintained to the close to the 34th week, before reducing by approximately 25 percent (Gordon n.d.). However, the hepatic blood flow remains normal, but like the high RBF, GFR also increases in the 2nd trimester. In contrast to the RBF, which is scientifically proved to fall between the week 26 and 36 of pregnancy, the GFR is measured 50 percent higher than non pregnant levels, and remains unchanged through pregnancy (Dunlop 1979). Both increases influence more of maternal excretion. Serum or the blood levels minimize in gestation, with the increased clearances in urea, creatinine, and uric acid. 6.3 Fluid and electrolyte homeostasis Hormones play an active role in decline of plasma osmolality. Instead, more water can be retained as progesterone, aldosterone, and renin-angiotesin concentration increases. Various nutrients are soluble in the water and as it is retained back, some of these nutrients are reabsorbed back. One of them is Sodium content, which is a major determinant of volume homeostasis. According to Odutayo and Hladunewich, by the end of gestation, overall body potassium and sodium increases by up to 320 mEq/d and by a mean of 3– 4 mEq/d, ending in a net balance of 900–1000 mEq respectively (2012). Potassium (K+) retention is stimulated by hormone progesterone level, which increases the kidneys ability to conserve extra potassium. Sodium re- absorption in the proximal and distal tubules is facilitated by increase in aldosterone, estrogen, and cortisol levels that cause glomerulotubular changes. As a result, the factors (e.g. GFR, progesterone, and decrease in plasma albumin) that influence sodium excretion are exceeded and the excretion activity of sodium is intercepted by those (hormones) promoting retention, enough to favour net Sodium (Na+) re-absorption. 7.0 Summary Generally, maternal body and internal system functions respond with the development of a pregnancy. Changes in the reproductive system are essential to cater for the functioning of foetal organs and its structure maturation in size. These adaptations not only support the pregnancy, but also the maternal system functions. The respiratory system has to adjust in inhalation and exhalations facilitated by changes in chest circumference and upward push of the diaphragm. The foetal demands contribute to the increased demand of oxygen because of its metabolic process and excretion. Cardiovascular adaptations follow the upward and left shift of the heart due to pregnancy exertion on the diaphragm. While the blood volume and cardiac output increases, systemic blood pressure reduces. The maternal renal system also goes through anatomical and structural changes in the kidney and the collecting system to cause renal vasodilatation, resulting in increase of RBF. All these changes, whether they persist along pregnancy or change with the transition of the trimester, are normal adaptations to meet the maternal and foetal demands. Appendix PaCO2 –Partial pressure of carbon IV oxide in the arterial blood PaO2 - Partial pressure of oxygen in the arterial blood RBF –Renal blood flow GFR –Glomerular filtrate rate Reference List American Medical Association n.d., ‘Female Reproduction Pregnancy’, retrieved 3October 2013, . Bruck, L 2008, Maternal-Neonatal Nursing Made Incredibly Easy! , 2nd ed, Lippincott Williams & Wilkins, Ambier. Campbell, L A & Klocke, R A 2001, ‘Implications for the Pregnant Patient’, American Journal of Respiratory and Critical Care Medicine, vol.163, no. 5, pp. 1051-1054. Chandra, S, Tripathi, A K, Mishra, S,Amzarul, M & Vaish, A K 2012, ‘ Physiological Changes in Hematological Parameters during Pregnancy’, Indian J Hematol Blood Transfus, vol. 28, no. 3, pp. 144–146. Datta, S, Kodali, B S & Segal, S 2010, ‘Maternal physiological Changes, during Pregnancy, Labour, and the Postpartum Period’, retrieved 3 October 2013, . Dunlop, W 1979. ‘Renal Physiology in Pregnancy’, Postgraduate MedicalJournal, vol. 55, no. 643, pp. 329–332. Forbes, K & Westwood, M n.d., ‘Maternal Growth Factor of Human Placental Development and Foetal Growth’, Journal of Endocrinology, vol. 2010, no. 207, pp. 1-16. Gordon, M C n.d., ‘Maternal Physiology’, retrieved 3 October 2013, . 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