Women in the fentanyl groups experienced less sedation ( i.n. fentanyl @ % , s.c. fentanyl @ % , i.m. pethidine @ % ; P @ ) , shorter labours by at least @ hours ( P < @ ) , and fewer difficulties establishing breastfeeding ( @ % i.m. pethidine , @ % i.n. fentanyl , and @ % s.c. fentanyl ; P < @ ) .