Compared to the 38 weeks group , the women in the 39 weeks group were more likely to have an unscheduled caesarean section ( 15.2 % vs. 9.3 % ; RR 1.64 , 95 % CI 1.21 ; 2.22 ) , to deliver between 6 pm and 8 am ( 10 % vs. 6 % ; RR 1.68 , 95 % CI 1.14 ; 2.47 ) , or to have the procedure rescheduled ( 36.7 % vs. 23 % ; RR 1.6 , 95 % CI 1.34 ; 1.90 ) .