Prevalence of VDD in the 800-IU group was significantly lower than in the 400-IU group at 40 weeks ( 38.1 % vs. 66.7 % ; relative risk : 0.57 ; 95 % confidence interval : 0.37-0 .88 ) and at 3 months ' CA ( 12.5 % vs. 35 % ; relative risk : 0.36 ; 95 % confidence interval : 0.14-0 .90 ) .