“…The incidence of these malformations in a population shows striking variations depending on ethnic, geographical and seasonal and social factors (Persaud and Persaud, 1982;Cocchi et al, 1995;Shaw et al, 1997). Nutritional folic acid de ciency plays an important role in the origin of these malformations (Czeizel and Dudas, 1992;Czeizel, 1994;Vigan et al, 1996), possible roles of increased temperature exposure (high fever, sauna) (Shaw et al, 1998), other teratogenic agents (Kallen, 1998) or maternal age (Janerich, 1972;Elwood et al, 1978;Borman et al, 1986;Dudin, 1997) are also considered.…”