PHYSIOLOGICAL CHANGES IN PREGNANCY

Physiological changes in Pregnancy : 

1 December 2008 1 Physiological changes in Pregnancy Dr. ANISH JOSHI

Changes in uterus : 

1 December 2008 2 Changes in uterus Uterine blood flow increases from 50 ml/ min to 700 – 800 ml /min Uterine weight increases from 30-60 g to 1000 g

Uterine blood flow : 

1 December 2008 3 Uterine blood flow Uteroplacental vascular bed is passive capacitance bed Intervillous blood flow exhibits no auto regulation UBF dependent on MAP, aorto-caval compression & C.O

CVS : 

1 December 2008 4 CVS Intravascular fluid volume: + 35% Plasma volume: + 45% Erythrocyte volume: + 20% Cardiac Output: + 40% Stroke volume: + 30% Heart rate: + 15% Peripheral Circulation: Systolic BP: no change Diastolic BP: - 15% MAP no change Systemic Vascular Resistance: - 15% Femoral venous pressure: + 15%

CVS : 

1 December 2008 5 CVS In supine position the gravid uterus compresses the IVC and decreases the CO without fall in the blood pressure called as Concealed caval compression/syndrome. Reasons for no fall in blood pressure are: Reflex vaso constriction Diversion of blood through paravertebral venous plexus

CVS : 

1 December 2008 6 CVS Overt Caval Compression (supine hypotensive syndrome) Hypotension Sweating Bradycardia Pallor Nausea Vomiting Prevention Left lateral tilt 15 degrees Placing wedge under the right buttock

CVS : 

1 December 2008 7 CVS Poseiro Effect: Uterine artery is compressed during uterine contractions & by the presenting part of the fetus reducing the UBF

CVS : 

1 December 2008 8 CVS Heart Size: Gravid uterus pushes the diaphragm cepahalad & displaces the heart. ECG: LAD CXR: False cardiomegaly

RS : 

1 December 2008 9 RS MV: + 50% TV: + 40% RR: + 10% FRC: - 20% ERV: - 20% RV: - 20% Oxygen consumption: + 20%

Slide 10: 

1 December 2008 10

RS : 

1 December 2008 11 RS Edematous mucosa of upper resp tract: Smaller ET tubes Gentle suctioning & larngoscopy Increased O2 consumption: Pre-oxygenation prior to induced apnea

Blood : 

1 December 2008 12 Blood Fibrinogen, factors VII, VIII and X increased Makes the blood hypercoaguable & increases the risk of thromboembolism This hypercoaguability along with uterine inversion helps in reducing blood loss after delivery

GIT : 

1 December 2008 13 GIT Decrease in lower oesophageal tone Delay in gastric emptying: Pylorus is pushed upwards & forwards making it non-dependent Relaxant effect on gastric smooth muscle Increased intragastric pressure

Liver / GB : 

1 December 2008 14 Liver / GB LFTs: N Serum cholinesterase activity  Biliary gall stones

Renal system : 

1 December 2008 15 Renal system ↑ RBF, GFR & Creatinine clearance ↑ Tubular reabsorbtion rate Blood Urea Nitrogen 40% 

Metabolism & Nutrition : 

1 December 2008 16 Metabolism & Nutrition BMR: ↑ by 15 to 20% Weight gain upto 11 kgs Serum protein & albumin concentration ↓ Drugs are less bound to serum proteins thereby increasing the free drug availability

Placental functions : 

1 December 2008 17 Placental functions Metabolism Endocrine secretion Human chorionic gonadotrophin Human chorionic somatotrophin Progesterone Estrogen Molecular transfer

Placental blood flow : 

1 December 2008 18 Placental blood flow Placental Blood Flow = 500-700ml/min ( approximately 10% of the Cardiac output) Maternal BP & c.o Vasomotor tone of the uterine vessels Pathological changes of the placenta State of uterine contraction

Slide 19: 

1 December 2008 19 Thank you