Women in the fentanyl groups experienced less sedation ( i.n. fentanyl 7.3 % , s.c. fentanyl 2.9 % , i.m. pethidine 44 % ; P 0.03 ) , shorter labours by at least 2 hours ( P < 0.05 ) , and fewer difficulties establishing breastfeeding ( 78.8 % i.m. pethidine , 39.4 % i.n. fentanyl , and 44.0 % s.c. fentanyl ; P < 0.01 ) .