Healthy paturients undergoing cesarean delivery with intrathecal morphine @g and fentanyl @g were randomized to receive : prophylaxis ( ondansetron @mg at cord clamping , normal saline @mL for treatment of pruritus in the post-anaesthesia care unit ) ; treatment ( normal saline @mL at cord clamping , ondansetron @mg as required in the post-anesthesia care unit ) or control ( normal saline @mL in both ) .