Vitamin A References:

Shaw GM, Velie EM, Schaffer D, Lammer EJ. Periconceptional intake of vitamin A among women and risk of neural tube defect-affected pregnancies. Teratology 1997;55:132-133

Shaw GM, Wasserman CW, Block G, Lammer EJ. High maternal vitamin A intake and risk of anomalies of structures with a cranial neural crest cell contribution (letter). Lancet 1996; 347:899-900