Ventilatory functions in pregnancy.

The apparatus used was a dry bellows spirometer and a Wright's peak flow meter. Statistical analysis using the student's t test showed a significant reduction in peak expiratory flow rate, forced vital capacity and first second forced expiratory volume in the third trimester compared to controls. Besides, mid-expiratory flow rates were significantly lower in the first trimester. Spirometric performance was reduced in all three trimesters when compared to controls, although values were within physiological limits. This reduction may assume importance in patients with associated diseases or those requiring surgery.