After tracheal intubation, subjects were allocated randomly to two groups by drawing sequentially numbered sealed opaque envelopes containing a software-generated randomisation code (Random Allocation Software, version 1.0.0, Isfahan University of Medical Sciences, Isfahan, Iran). The parturients in the placebo group (n = 183) received sublingual two moistened white coated placebo tablets which looked identical in size, colour, and packing to misoprostol tablet. In the misoprostol group (n = 183), sublingual misoprostol was given by putting two moistened tablets of misoprostol (400 µg) under the tongue and allowing them to dissolve (Misotac®, Sigma Pharmaceutical Industries, Egypt) (200 µg/tablet). The anaesthesiologists who gave the anaesthetics and study tablets were blinded to the study randomization and were not involved in collecting of the patients' data. All staff in the operating room were unaware of the randomization code.