Pregnancy-Physiology-10-08-07.ppt
Transcript of Pregnancy-Physiology-10-08-07.ppt
OBJECTIVE 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 are required for successful pregnancy.
Nearly every organ system is affected. Understanding these changes helps to
distinguish normal physiology from pathological disease states.
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 Elevation of maternal CO
OSMOREGULATION
Na retention increases 900 mEq but serum Na decreases 3-4 mmol/l
Plasma osmolality decreases 10 mOsm/kg Enhanced tubular reabsorption of Na
secondary to aldosterone,estrogen and deoxycorticosterone.
Increased GFR and Atrial Natriuretic Peptide favor Na excretion
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 Increase in left ventricular wall mass c/w mild
hypertrophy Increase in preload with increase capacitance of the systemic and pulmonary vascular resistances to prevent rise in CVP or wedge pressure.
Grade II-III systolic flow murmurs at left lower sternal border
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 TLC by 5% and
FRC by 20% FRC mainly decreased by RV Vital capacity does not change Spirometry is not changed in pregnancy
FEV1 is unchanged
Peak flow is unchanged
RESPIRATORY CHANGES
Chronic hyperventilation Progesterone induced Minute volume is increased Tidal volume is increased Respiratory rate is unchanged Increased early in the first trimester
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 nadiring at
30 weeks Increase in erythropoietin and reticulocyte
count
IRON METABOLISM Absorption in the duodenum in the divalent state Trivalent food source must be converted by ferric
reductase to divalent form Fe enterocytes bound transferrin
transported to liver, spleen, muscle and bone marrow incorporated into hemoglobin, myoglobin, ferritin or hemosiderin
1000mg iron requirement, about 3.5 mg/dL of Fe Requirements increase in third trimester Fetus receives Fe through active transport
FE SUPPLEMENTATION
Fe 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
Burrows @Kelton reported an 8% prevalence
Plts range between 70-150,000.
Diagnosis of exclusion
?PET/HELLP, ITP, viral disease, HIV, autoimmune disease, ie lupus
OTHER HEMATOLOGIC CHANGES
Leukocytosis secondary to neutrophils 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 tortuosity throughout the bladder leading to microhematuria
Decrease bladder capacity
Increased frequency of urinary incontinence
RENAL HEMODYNAMICS
Renal blood flow increases 50% GFR increases 50% (120cc/min180cc/m) Serum Creatinine and BUN levels decrease Glycosuria occurs due to exceeding of
maximum tubular reabsorptive capacity No increase in proteinuria
UTI
Pre-existing renal disease
PET
DIGESTIVE TRACT CHANGES
Addition of 300 kcal/day Gingivitis of pregnancy
Violaceous pedunculated lesion
Epulis gravidarum Stomach
Delayed emptying during labor
Gastroesophageal reflux disease (GERD)
Esophageal dysmotility
Gastric 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
Increased portal hypertension leading to dilation wherever there are portosystemic venous anastomoses
Gallbladder Decreased rate of emptying due to
progesterone Cholesterol saturation is increased while
chenodeoxycholic acid is decreased in bile favoring stone formation
Liver Size and histology are unchanged Clinical and laboratory changes mimic disease
states Spider angiomas and palmar erythema Serum albumin and total protein decrease Serum alkaline phosphatase activity Other LFT’s are unchanged
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 Decrease in circulating pool of extra-thyroidal
iodide Slight thyromegaly Free T4 and T3 remain normal Small amounts of TRH @T4 cross the placenta 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 insure
continuous transport of nutrients from mother to fetus
Fasting hypoglycemia Postprandial hyperglycemia Hyperinsulinemia
FUEL METABOLISM
Pregnant prolonged fasting Increased utilization of fat stores Lipolysis generates glycerol, fatty acids and
ketones for gluconeogenesis and fuel More HPL, less insulin results in increased
utilization of fat stores Maternal response to starvation
Hypoglycemia, hypoinsulinemia
Hyperlipidemia, hyperketonemia
Maternal response to feeding
Hyperglycemia,
Hyperinsulinemia,
Hyperlipidemia,
Resistance to insulin Insulin secretion increases throughout Insulin resistance increases to 50-80% in third
trimester Borderline pancreas function leads to GDM
ENDOCRINE CHANGES
Diabetogenic effects of pregnancy
HPLlipolytic and anti-insulin
Cortisol
Prolactin
Estrogen and progesterone Fetal glucose levels are 20 mg/dL less than
maternal values Placental glucose transport is carrier mediated
facilitated transport that is energy independent
FUEL AND METABOLISM
Lipids and lipoproteins increase in pregnancy Total cholesterol, LDL, HDL and triglycerides
all increase Necessary as precursors for steroidogenesis Does not appear to lead to atherosclerosis
unless pre-existing hyperlipidemia
PLACENTAL TRANSPORT OF NUTRIENTS
INTEGUMENTAL CHANGES
Hyperpigmentation 90% of pregnancies Localized to areas of increased melanocytes Choasma of pregnancy
70% of women
All races
Up to 30% of changes can persist
Hair Changes Mild hirsutism is common Excessive virilization should prompt
investigation for androgen-secreting tumors Normal pregnancy increases amount of hair in
anagen phase(growth) Postpartum, telogen effluvium may occur with
increased amount of hair in resting phase which leads to loss
OCULAR CHANGES
Increased thickness of the cornea Edema induces a 3% increase Affects contacts
Decreased intraocular pressure Glaucoma improves Minimally decreases visual fields