Pregnancy-Physiology-edited-13-09-10.ppt
Transcript of Pregnancy-Physiology-edited-13-09-10.ppt
On the Brink of Birth
A full term fetus, is shown in its mother’s womb in this Leonardo da vinci drawing. One of the first accurate renderings of a part of the human anatomy. The smaller sketches depict details of the uterus. Of all the triumphs of the body, its crowning glory is the power to reproduce its kind and pass some of its hereditary characteristics on to later generations.
Embryo to Fetus
fifteen days twenty-one days thirty days thirty-four days six wks eight wks
Life: One Seed + One Egg Life begins when an egg, previously released from one of the two ovaries, merges with just one of the hundreds of millions of sperm cells supplied through the vagina by the male reproductive system. The fertilized egg then descends to the wall of the uterus, where it implants itself to begin gestation.
Fetus
The average weight of the Indian baby at 40 weeks of
pregnancy is 2,750Gms at birth.
New Born
A healthy new born cries vigorously as soon as he is born, kicking his limbs actively, giving the greatest joy to the tired mother.
INTRODUCTION
Pregnancy causes physiologic changes in all maternal organ systems; most return to normal after delivery.
In general, the changes are more dramatic in multifetal than in single pregnancies.
Major adaptations in maternal anatomy, physiology, and metabolism.
BODY WATER METABOLISM
Condition of chronic water overload
Active Na and water retention
1. Changes in osmoregulation
2. Renin-angiotensin system
Body water increase 6.5L 8.5L
1. 1500 cc increase in blood vol
2. RBC increase ~400cc
OSMOREGULATION
Na retention increases 900 mEq but serum Na decreases 3-4 mmol/l
Plasma osmolarity decreases 10 mOsm/kg
Enhanced tubular reabsorption of Na secondary to aldosterone,estrogen and deoxycorticosterone.
CARDIOVASCULAR CHANGESHeart Displaced to the left and upward Apex is moved laterally Apparent cardiomegaly on chest x-ray Increase in left ventricular end-diastolic dimension Cardiac output (CO) increases
RESPIRATORY CHANGESUpper Respiratory Tract Hyperemia and edema induced by estrogen Nasal stuffiness and epistaxis
Mechanical changes
earlier than mechanical pressure of rising uterus Chest circumference expands 5-7 cm Subcostal angle increases from 68 to 103 degrees Transverse diameter increases 2cm Level of diaphragm rises 4cm but excursion is not
impeded Respiratory muscle function is not affected by
pregnancy
LUNG VOLUME AND PULMONARY FUNCTION
Elevation of the diaphragm decreases the volume of the lungs in the resting state, reducing Total Lung Capacity (TLC) by 5%
Functional Residual Capacity (FRC) by 20% FRC mainly decreased by Residual Volume (RV)
Vital capacity does not change Spirometry is not changed in pregnancy
Forced Expiratory Volume in 1 sec (FEV1) is unchanged
Peak flow is unchanged
HEMATOLOGIC CHANGES
40-50% increase in blood volume beginning at 6 weeks and plateaus at 30 weeks
Both plasma volume and cell mass increase
Physiologic anemia of pregnancy at 30 weeks
Increase in erythropoietin and reticulocyte count
IRON METABOLISM Iron (Fe) bound transferrin transported to
liver, spleen, muscle and bone marrow incorporated into hemoglobin and myoglobin
1000mg iron requirement, about 3.5 mg/dL of Fe
Requirements increase in third trimester
Fetus receives Fe through active transport
IRON SUPPLEMENTATION
Iron supplementation usually not needed before 20 weeks
30mg of elemental FE 325 mg ferrous gluconate
Fe supplements
Ferrous sulfate ( 65mg elemental Fe)
Ferrous gluconate (35mg of elemental Fe)
PLATELETS
Progressive decline in count from 1st-3rd tri
Increased platelet destruction
Gestational thrombocytopenia of pregnancy
OTHER HEMATOLOGIC CHANGES
Leukocytosis secondary to neutophils Estrogen induced Cortisol induced
Altered immune status Modulation away from cellular immunity
towards humoral immunity Paradoxical decline of immunoglobins A,G,M Only IgG crosses the placenta
URINARY SYSTEMAnatomic Changes Renal hypertrophy Dilation of renal pelvis/calyces
15mm on the right in 3rd trimester
5mm on the left
Predisposition to pyelonephritis in the presence of asymptomatic bacteriuria
Dilation of ureters to 2 cm Mechanical compression Progesterone-induced smooth muscle
relaxation
BLADDER CHANGES
Bladder trigone elevation occurs with increased vascular tortuousity throughout the bladder leading to microhematuira
Decrease bladder capacity
Increased frequency of micturition.
DIGESTIVE TRACT CHANGES
Addition of 300 kcal/day Gingivitis of pregnancy Stomach
Gastroesophageal refluxGastric compression due to enlarging
uterus
Decrease sphincter tone
Small bowel
Motility is reduced due to progesterone allowing for more efficient absorption
Large bowel
Decreased transit times allows for both water and sodium absorption
Liver Size and histology are unchanged Clinical and laboratory changes mimic disease
states Palmar erythema
SKELETAL AND POSTURAL CHANGES
Lordosis of pregnancy~ progressive increase in anterior convexity of the lumbar spine
Preserves center of gravity
Ligaments of the symphysis and sacroiliac joints loosen during pregnancy due to relaxin
ENDOCRINE CHANGES
Thyroid Physiology Euthyroid state Increase in thyroxine-binding globulin Slight thyromegaly T4 and T3 remain normal Fetal thyroid active by 12 weeks gestation
Adrenal function Increases in corticosteroid-binding globulin Increases in free cortisol Zona fasciculata is increased Marked increase in CRH from placental
sources Delayed plasma clearance of cortisol due to
renal changes Resetting of hypothalamic-pituitary sensitivity
to cortisol feedback on ACTH production
Pituitary gland Enlarges due to proliferation of prolactin-
secreting cells Enlargement makes it more susceptible to
alterations in blood flow, ie PPH Prolactin levels are increased (ten times higher
at term) to prepare breasts for lactation
Pancreas and Fuel Metabolism Physiologic glucose intolerance to ensure
continuous transport of nutrients from mother to fetus
Fasting hypoglycemia Postprandial hyperglycemia Hyperinsulinemia
Diabetogenic effects of pregnancy
Cortisol
Prolactin
Estrogen and progesterone
Fetal glucose levels are 20 mg/dl less than maternal values
INTEGUMENTAL CHANGES
Hyperpigmentation 90% of pregnancies
Localized to areas of increased melanocytes
Chloasma of pregnancy