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physiologic changes in pregnancy

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Beverly Wudel

on 27 September 2012

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Transcript of physiologic changes in pregnancy

Cardiovascular Changes During Pregnancy Review the physiologic changes that occur during normal pregnancy
Identify challenges that these normal physiologic changes present in evaluating the pregnant patient
Review some of the medical conditions which present high maternal risk Objectives diaphragm rises 4cm
subcostal angle increases
net effect is reduced lung volume Anatomical Changes of the Respiratory Tract O2 consumption increases by 20%
rise in minute ventilation is disproportionate to the increase in O2 consumption
PaO2 100-110 mmHg
PaCO2 27-32 mmHg
HCO3 ~22 mmol/L
pH 7.4-7.45
maternal hypocarbia aides CO2 transfer across placenta to maternal circulation Changes in gas exchange Endocrine adaptations Hypothalamic hormones:

Increased Gonadotropin releasing hormone (GnRH) produced in the placental tissue

Increased Corticotropin releasing hormone (CRH) produced by placenta, chorionic trophoblasts, amnion, and decidual cells Pituitary hormones:

gland enlarges about 3x

Increased growth hormone
levels are linked to development of preeclampsia, maternal insulin resistance, and fetal birth weight

Increased prolactin
stimulates hyperplasia of glandular epithelial cells and presecretory cells of the breast

Also changes in ACTH, MSH, oxytocin, and ADH sensitivity and metabolism Endocrine adaptations Thyroid Hormone:
Thyroid hyperplasia
Increased total thyroxine and thyroxine binding globulin
TSH, free T3, T4 levels normal
No apparent effect on maternal metabolic rate

Parathyroid Hormone:
Increased plasma volume results in relative decrease in plasma Ca
Physiologic hyperparathyroidism
Facilitates activation of 1,25-OH vitamin D
Increased estrogen and calcitonin levels protect skeletal calcification Endocrine Adapatations Adrenal:

Cortisol levels increased in response to increased ACTH and decreased metabolic clearance

Aldosterone levels are increased in response to RAAS stimulation by decreased vascular resistance and blood pressure Endocrine Adaptations Carbohydrate metabolism:

Placental secretion of growth hormone, corticotropin releasing hormone, human placental lactogen and progesterone cause maternal insulin resistance and hyperinsulinemia

Prolactin and HPL stimulate hyperplasia of the beta cells of the pancreas Metabolic Adaptations Lipid metabolism:

Increased plasma lipids and lipoproteins
High triglycerides provide maternal fuel source
High LDL increases placental steroidogenesis

Protein metabolism:
accumulation of about 1kg of protein
more efficient use of dietary protein Metabolic Adaptations Immunologic:
Suppression of humoral and cell-mediated immunity
may explain pregnacy-related suppression of RA, MS, autoimmune thyroiditis
Neutrophil activation impaired by relaxin
Increased inflammatory markers - CRP, ESR, C3, C4 Hematologic Adaptations Hemostasis:
increased coagulation and fibrinolysis
increased clotting factors (except XI, XIII), HMW fibrinogen complexes
decreased platelets
Decreased activated protein C & S Hematologic Adaptations Reproductive
Kidneys & Urinary
Musculoskeletal Physiologic Adaptations in Pregnancy: Blood volume:
40-45% increase in blood volume
plasma volume > erythrocyte volume
increase reticulocyte count
decreased hematocrit Hematologic Adaptations Gastroesophageal reflux (30-50%)
decreased LES tone
displacement of stomach by uterus
Gastric emptying time
prolonged during labour and administration of analgesics
high risk of aspiration during labour and general anaesthesia Esophagus & Stomach Anatomical changes
displaced upwards by uterus
Abnormal laboratory findings:
decreased albumin
increased ALP (2-4 times normal)
increased triglycerides and total cholesterol

decreased contractility (progesterone)
increased cholesterol concentration in bile
increased risk of cholelithiasis, intrahepatic cholestasis Liver & Gallbladder Bloating and constipation
decreased transit time
mechanical obstruction of gravid uterus

Hemorrhoids (30-40%)
increased venous pressure
constipation Small & Large Bowel Cardiac output increases by 30-50%
↑ preload
↓ afterload
↑ heart rate
Changes in physical exam:
↑ JVP, basilar crackles, exaggerated heart sounds, new SEM, physiologic S3, peripheral edema
ECG changes:
increased rate
shortening of PR and QT intervals
non-specific alterations in ST segments and T-waves
up to 20 degrees of LAD Cardiac output up to 80% higher than third trimester
↑ preload
↑ heart rate & blood pressure
relief of venacaval obstruction Cardiovascular Changes During Labour & Delivery Severe AS
Symptomatic MS (NYHA Class II-IV)
AR or MR (NYHA Class III-IV)
Aortic or Mitral valve disease with severe LV systolic dysfunction or severe pulmonary hypertension
Marfan syndrome
Mechanical prosthetic valve requiring anticoagulation
Pulmonary HTN (>80mmHg)
Eisenmenger's syndrome (L to R shunt) High-risk Cardiopulmonary Lesions increased size of kidney
dilatation of ureters and renal pelvis
increased GFR
physiologic hyponatremia
decreased tubular absorption
increased metabolic clearance of ADH Adaptations in the Kidney and Urinary Tract Risks of pregnancy in CKD decline in kidney function in women with pre-existing renal disease
50% risk of permanent exacerbation of renal disease if serum creatinine >130 at baseline
increased risk of gestational hypertension, pre-eclampsia, death
increased risk of premature delivery, IUGR, SGA, stillbirth Physiologic Changes in Pregnancy Pregnancy induces physiologic changes in every system
The physiologic changes in pregnancy affect pre-existing disease, which may result in adverse maternal and fetal outcomes
Knowledge of normal physiologic changes in pregnancy is essential in evaluation of pregnant women for medical disease Summary Questions? Cunningham, FG. Williams Obstetrics 23 Ed.
Siu SC, Sermer M, Harrison DA et al. Risk and predictors for pregnancy-related complications in women with heart disease. Circulation. 1997;96(9):2789.
Vahanian A, Baumgartner H, Bax J, et al. 2008 Focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. 2008;118(15):e523.
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