- Periconceptual vitamin use among Mexican American case women with neural tube defect-affected pregnancies and control women in 14 Texas-Mexico border counties, 1995-1999

- Vitamin use was defined as maternal use of multivitamins, prenatal vitamins, or single ingredient folic acid tablets from 3 months before conception to 3 months after conception

- Only 11 case and 10 control women reported daily use of folic acid-containing vitamins throughout the entire preconception period