“…Our results were in line with previous studies (Douglas and Levinson, 2001;Faddy and Garlick, 2005;Rooks, 2007;Latto et al, 1973;Bishop, 2007;Evans et al, 1995;Jones et al, 1969;McAneny, 1963). However, in contrast, one prospective non-randomized study, labor pain was more severe in primi-gravid women that were administered nitrous oxide as compared to those that were given pethidine (Keskin et al, 2003).…”