Physiologic changes in pregnancy

Respiratory:increased minute ventilation with chronic respiratory alcalosis, reduction of functional residual capacity, difficult airway (weight gain, edema of upper airway and vocal cord)

Cardiac changes: increased cardiac output, decresed systemic and pulmonary vascular resistance; aortocaval compression with supine hypotension 

Hematologic changes:  blood volumen expansion, dilutional anemia; benign leukocitosis (up to 15000in pregnancy and up to 20000 in labour); hypercoagulable state with high risk for thromboembolism

Gastrointestinal system:  reduction in lower esophageal sphincter tone, mechanical change of the angle of the gastroesophageal sphincter; increase in gastric acidity; muscle dysrrythmia with nausea, vomiting;

Central and peripheral nervous system: increased sensitivity to volatile anesthetics and local anesthetics; reduced volume of epidural and subarachnoid space 

References

Nı´ Mhuireachtaigh R, O’Gorman D: Anesthesia in pregnant patients for nonobstetric surgery. Journal of Clinical Anesthesia (2006) 18, 60–66