Cardiovascular System
Total blood volume increased by about 40% due to retention of sodium and water during pregnancy, this accounts for a total body water increase of 6 to 8 liters!
1st Trimester: Plasma volume rises as early as the 6th week and plateaus by the 32-34th week.
2nd Trimester: Red blood cell mass begins to increase. Due to the higher increase in plasma volume compared to red blood cell volume, hemodilution with a decreased hematocrit reading, known as physiological anemia or pregnancy.
Cardiac output rises by the 10th week and reaches about 40% above non-pregnant levels by 20-24 weeks.
Oxygen consumption is higher in pregnant than in non-pregnant women.
Systolic pressure falls only slightly during pregnant, whereas diastolic pressure decreases more markedly; this decrease begins in the first trimester, reaches its nadir in mid-pregnancy, and returns toward non-pregnant levels by term.
The venous compression by the gravid uterus elevates pressure in the veins that drain the legs and pelvic organs, thereby exacerbating varicose veins in the legs and vulva and causing hemorrhoids.
Two of the major increases in regional blood flow, to the kidney and skin, serve purposes of elimination: the kidney of waste material and the skin of heat.
When maternal cardiac output falls, blood flow to the brain, kidney and heart is supported by redistribution of cardiac output, which shunts blood away from the uteroplacental circulation.
Desite the relatively low "optimal" hematocrit, the arteriovenous oxygen difference in pregnancy is blow non-pregnant levels. This supports the concept that the hemoglobin concentration in pregnancy is more than sufficient to meet oxygen-carrying requirements.
Respiratory System
As pregnancy progresses, the enlarging uterus elevates the resting position of the diaphragm, resulting in a decreased resting lung volume.The vital capacity remains unchanged.
Total body oxygen consumption increases by about 15-20% in pregnancy.
In pregnancy, the elevations in both the cardiac output and alveolar ventilation are greater than those required to meet the increased oxygen consumption.
The rise in minute ventilation reflects an approximate 40% rise in tidal volume at term; the respiratory rate does not change during pregnancy.
Increased respiratory sensitivity to CO2 is characteristic of pregnancy and probably accounts for the hyperventilatin of pregnancy.
Pregnancy is characterized by hyperventilation and is associated with respiratory alkalosis.
Despite the absence of obstructive or restrictive effects, dyspnea is a common symptom in pregnancy. Some studies have suggested that dyspnea may be experienced at some time during pregnancy by as many as 60-70% of women.
Renal System
As the uterus enlarges, partial obstruction of the ureters occurs at the pelvic brim in both the supine and upright position.
Renal plasma flow and glomerular filtration rate increase early in pregnancy and achieve a plateau at about 40% above non-pregnant levels by mid-gestation then remain unchanged to term.
Pregnancy causes compensated respiratory alkalosis with chronic losses of fetal bicarbonate.
The maternal extracellular volume, which consists of intravascular and interstitial components, increases throughout pregnancy, leading, in effect, to a state of physiologic extracellular hypervolumia.
Renin levels remain elevated throughout pregnancy.
Insulin effects and glucose metabolism
In pregnancy, the insulin response to glucose stimulatinon is augmented.
Glycogen synthesis and storage by the liver increases, and gluconeogenesis is inhibited.
After early pregnancy, insulin resistance emerges, so glucose tolerance is impaired. The fall in serum glucose for a given dose of insulin is reduced compared with the response in early pregnancy.
A variety of humoral factors have been suggested to account for the anti-insulin environment of the latter part of pregnancy. Perhaps the most important is human placental lactogen.
Lipid Metabolism
During the second half of pregnancy, probably as a result of rising human placental lactogen levels, lipolysis is augmented, and the plasma concentration of free fatty acids after an overnight fast is elevated,
In the context of maternal lipid metabolism, the mostdramatic lipid change in pregnancy rise in fasting triglyceride concentration.
Thyroid
The thyroid glad undergoes moderate enlargement during pregnancy.
Thyroxine-binding globulin is increased during pregnancy because the high estrogen levels induce increased hepatic synthesis.
Adrenal Gland
Adrenocorticotripic hormone (ACTH) and plasma cortisol levels are both elevated from 3 months gestation to delivery.
Unlike the level of thyroid hormones, the mean unbound level of cortisol is elevated in pregnancy.
Immunological response during normal pregnancy
The nonspecific (innate) mechanisms of the immunological system (including phagocytosis and the inflammatory response) are not affected by pregnancy. The specific (adaptive) mechanisms of the immune response (humoral and cellular) are also not significantly affected.
Maternal IgG is the major component of fetal immunoglobulin in utero and in the early neonatal period. IgG is the only immunoglobulin that is transported across the placenta.
The above information was taken directly from:
Hacker, N., Gambone, J. & Hobel, C. (2010) Essentials of Obstetrics and Gynecology: 5th Edition. Philadelphia, PA: Saunders Elsevier.
The nervous system
Brain cells shrink during pregnancy resulting in lessened cognitive ability. Short periods of depression are common and many women lack confidence.
Fatigue during the first trimester.
Numbness and tingling of the fingers and hands as a result of edema pressing on the median nerve, a condition known as carpal tunnel syndrome.
Headaches are common during the first week postpartum and are likely due to tension.
Endocrine System
Many of the alterations in endocrine activity during pregnancy match changing body needs.
Early symptoms of pregnancy, changes in appetite, sleep patterns and food tolerance are thought to be a result of the increased level of human chorionic gonadotrophin.
Estrogen levels rise during pregnancy and act on the liver to release proteins and cholesterol. They are required to ready the breast for lactation.
Progesterone levels increase threefold by term and act as a smooth muscle relaxant.
Relaxin is initially released by the corpus luteum and later by the placenta. Levels of this hormone are highest in the first trimester and it is thought to synergistically act with progesterone to inhibit conractility of the myometrium.
Special Senses
A mild corneal edema is not uncommon during pregnancy particularly during the 3rd trimester. This could result in minor vision problems because refraction is altered.
Changes in smell for odorous substances such as coffee and fried food may aggravate nausea and vomiting.
hearing and touch do not appear to change during pregnancy.
The integumentary system
Increased pigmentation of certain areas of the skin are common in the majority of women. This is in response to the increase in circulating hormones.
Nipples and areola of the breast become darker.
The linea alba will darken and become the linea nigra. Freckles, birth marks and recent scare may also darken.
Chloasma, or the pregnancy mask, may develo as a butterfly shape around the nose and cheeks. It is caused by increased production of melanocyte-stimulating hormones of the anterior pituitary gland.
Stretch marks, or stria gravidarum, occur on areas that "over-stretch" the elastin fibers of the skin causing 'tears.'
Increased itchiness during pregnancy, pruritis gravidarum, is either generalized or felt over the abdomen and is of unknown origin. It usually disappears spontaneously after delivery.
Increased activity of the sebaceous glands, due to elevated hormones of pregnancy, may cause a feeling of greasiness.
Lymphatic System
Increased workload during pregnancy due to the increased blood volume.
Progesterone acts on the smooth muscles of the blood vessels causing an increase in the amount of tissue fluid. Slow to return fluid results in edema especially in the lower limbs.
The number of white blood cells increase, enhancing the non-specific mechanisms for destroing invaders.
Complement proteins are present in greater numbers but natural killer cells are reduced to protect the fetus and placenta from rejection.
The muscoluskeletal system
Progesterone and relaxin act on the cartilage and connective tissue of many joints allowing them more movement. May result in change in gait.
Backache may result from the relaxation of the sacroiliac joint and is aggravated by changes in posture.
Abdominal muscles become greatly stretched during pregnancy. May result in the separation of the recuts abdominus muscles during the third trimester.
The digestive system
Morning sickness is the nausea with vomiting sometimes associated with early pregnancy. May occur up to the 16th week.
Heartburn is caused by the regurgitation of stomach contents, which occurs because of the relaxation of the cardiac sphincter under the influence of progesterone.
Constipation is another side effect of the increased level of progesterone.
The above information was taken directly from:
Wylie, L. (2005) Essential Anatomy and Physiology in Maternity Care: 2nd Edition. Philadelphia, PA: Elsevier Churchill Livingstone.
