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We know that 400 μg of folic acid daily in early pregnancy reduces risk for neural tube defects. However, in 2000, Shaw and colleagues found that risk for having an infant with multiple congenital anomalies (MCAs) was increased in women who ingested periconceptional multivitamins containing folic acid (Am J Med Genet 2000; 93:188). Intrigued by this finding, CDC researchers conducted a similar analysis using data from the Atlanta Birth Defects Risk Factor Surveillance study. Cases were 96 infants born from 1993 through August 1997 with at least two major birth defects affecting different organ systems (chromosomal abnormalities, known single-gene disorders, and fetal alcohol syndrome were excluded). Controls were 334 infants with no birth d…