Physiologic Changes of Pregnancy PDF

# Physiologic Changes of Pregnancy ## Blood Supply to Uterus - Blood supply pre pregnancy = 10mls/min - At 40 weeks 800 - 900mls/min - 20% of cardiac output goes to uterus - Blood volume: from 5 litres to 7.5, total volume up by 40-50% - Red cell mass: rises constantly throughout pregnancy. Up by...

# Physiologic Changes of Pregnancy ## Blood Supply to Uterus - Blood supply pre pregnancy = 10mls/min - At 40 weeks 800 - 900mls/min - 20% of cardiac output goes to uterus - Blood volume: from 5 litres to 7.5, total volume up by 40-50% - Red cell mass: rises constantly throughout pregnancy. Up by 20% by end of pregnancy. ## 3rd Trimester - Lower segment formed from isthmus and contains longitudinal fibres - Upper segment thick and contains oblique muscle fibres - By 36 weeks lower segment measures 8-10cms - Engagement - By 38 weeks the cervix is taken up into the lower segment ## Blood Changes - Increase in oestrogen: new blood vessels formed, growth of existing ones - Therefore an increase in blood volume. ## By 12 Weeks - Uterus is upright and leans slightly to the right - No longer a pelvic organ - Uterus may be palpable above the pubic bone - Fetus now occupies most of the uterine cavity - Placenta now developed ## 2nd Trimester - Development of the upper and lower uterine segment - Upper segment, thicker containing oblique muscles - Lower segment formed from the isthmus contains circular and longitudinal muscles - Uterus is pear shaped again - Braxton Hicks contractions ## Changes in Size - Uterus grows to 30x23x20 at term - Weight increases to 900gms - Hypertrophy: Oestrogen causes cells to increase until 20 weeks gestation - Hyperplasia: number of cells increase under the influence of oestrogen ## After 20 Weeks Gestation - Uterine muscle tissue stretches to allow fetus to grow - Progesterone relaxes the smooth muscles enabling it to stretch ## Changes in the Shape of the Uterus - Isthmus elongates during the 1st 10 weeks like a stalk - From 7mm to 2.5cms at 10 weeks - Later becomes the lower segment with the globular uterus sitting on top ## Organisation of Muscle Fibres - Inner circular layer: surrounds cornua, lower uterine segment and cervix - Middle layer: oblique, crisscross arrangement involved in contractions to expel fetus - Outer longitudinal layer: contracts and retracts thickening the upper segment ## Physiologic Changes in Pregnancy - Reproductive System - Uterus: enlarges, especially fundal area thickens, then thins later in pregnancy. Umbilicus by 20 weeks, xyphoid by 36 weeks fundus, Braxton-Hicks irregular contractions after 4 months. - Cervix: mucous plug, Goodell's sign, Chadwick's sign - Ovaries: after 11 weeks, the placenta produces progesterone and estrogen ## Changes in the Cervix - Length remains the same - Increase in width - Softening after the third month due to oestrogen - Increased vascularity - Increased cervical mucosa - Increased glandular function ## Metabolic Changes - Increases in: - Insulin Level - Carbohydrate utilization during exercise as weight increases - Estrogen - Progesterone - Relaxin - Caloric requirements by ~ 300 calories/day - Protein and fluid requirements ## Genital Tract - Increased vascularity and hyperemia: vagina, perineum, vulva. - Increased secretions - Characteristic violet color of the vagina (Chadwick's sign) - Increased length of the vaginal wall - Hypertrophy of the papillae of the vaginal mucosa ## Digestive Changes - Digestive system slows - Intestines are pushed up and to the sides - Smooth muscle of the stomach relaxes and can cause heartburn. - Constipation and hemorrhoids are common during pregnancy. - Morning sickness ## Physiologic Changes - Metabolism - BMR increases by 20-25% during pregnancy. - Recommended weight gain – 25-35 lb - Overweight - 15-25 lb - Underweight – 25-35 lb - Need for increased iron, calcium, fat, and protein ## Physiologic Changes - Gastrointestinal - Digestive system slow due to progesterone - Nausea and vomiting - Ptyalism: increase salivation - Heartburn - Hemorrhoids - Prolonged gallbladder emptying time, which may lead to gallstones. - Bile salt buildup may lead to itching. ## Gastrointestinal Tract - Displacement of the stomach and intestines - Appendix can be displaced to reach the right flank - Gastric emptying and intestinal transit times are delayed secondary to hormonal and mechanical factors. - Pyrosis is common due to the reflux of secretions - Vascular swelling of the gums - Hemorrhoids due to elevated pressure in veins. ## Physiologic Changes - Respiratory System - Increase respiratory rate - Increased oxygen consumption - Common are nasal stuffiness, nosebleeds due to increased vascular swelling to nose ## Respiratory Consumption. - O2 consumption increases 15-20% - 50% of this increase is required by the uterus. - Despite increase in oxygen requirements, with the increase in Cardiac Output and increase in alveolar ventilation oxygen consumption exceeds the requirements. - Therefore, arteriovenous oxygen difference falls and arterial PCO2 falls. ## Cardiovascular Changes - Increase: - Blood volume - Cardiac (heart) output - Stroke volume - End Diastolic volume - Resting pulse - % of blood plasma - Decrease: - Hematocrit - Blood pressure - Blood supply to uterus - Cardiac reserve - Vascular resistance ## Cardiovascular System - Heart shifts up and to the left. - Hemoglobin stays the same (12-16 g/dL) initially. May drop down to 10 g/dL and still be normal physiologic anemia. - Normal pregnancy Hgb is 10-14 g/dL later in pregnancy - Decreased Hct (38-47%) - Normal pregnancy Hct is 32-42 later in pregnancy - Pulse rate may increase 10-15 beats. - Weight of uterus can cause supine hypotensive syndrome. ## Supine Hypotension Related to Venal Cava Syndrome ## Total Body Water - Increases 6-8 L - Increases by 40% - Normal body water: - 2/3 intracellular - 1/3 extracellular - ¾ interstitial - ½ intravascular - 2/3 increase is extravascular ## Physiologic Anemia of Pregnancy - Physiologic Intravascular change: - Plasma volume increases 50-70% beginning by the 6th week - RBC mass increases 20-35% beginning by the 12th week - Disproportionate increase in plasma volume over RBC volume----Hemodilution. - Despite erythrocyte production there is a physiologic fall in the hemoglobin and hematocrit readings ## Iron Deficiency Anemia ## Progesterone - Produced in corpus luteum and then the placenta - Relaxes smooth muscle - Inhibits uterine contractions until uterus is prepared for labor - Regulates storage of body fat ## Human Chorionic Gonadotrophic - Secreted from trophoblast of the developing embryo - Maintains corpus luteum until placenta takes over - Used in tests to confirm pregnancy ## Human Placental Lactogen ## Changes Are Due To - Alterations in: - Hormonal production - Circulation - Metabolism ## Hormones ### Oestrogen - Produced in corpus luteum - Produced by placenta after 12 weeks - Responsible for growth particularly of uterus and breasts ### Progesterone ## Changes to Body Systems ### First Trimester - Baby begins to grow - Increased urination - Changes with skin and hair - Thickening waistline - Nausea/fatigue ### Second Trimester - Baby's weight increases - Energy level improves - Heartburn - Leg cramps - Pelvis relaxes causing SI discomfort ### Third Trimester - Baby has more rapid growth and weight gain - Backaches - Swelling of the hands, legs, and feet - Breathlessness - More frequent urination ## Maternal Changes - Anatomical And Physiological - Cardiovascular Changes: - Increase in SV - Increase in Cardiac Output - Increase in HR at given work load - Increase in blood volume (mostly during latter half of pregnancy) - Uterus may compress large blood vessels reducing venous return - Total Body Water ## Circulatory