the prevalence of neural tube defects for women who used folic acid-containing multivitamins during the first 6 weeks of pregnancy was substantially lower -- 0.9 per 1000 ( prevalence ratio , 0.27 ; 95 % confidence interval , 0.12 to 0.59 compared with never users ) .
C0027794
neural tube defects
C0016410
folic acid