It has been proposed that the hyperthermia in pregnant women may be associated with birth defects in their offsprings. We analysed the retrospective interview data on probable febrile illness during critical period of orofacial clefts development in 992 mothers of boys and girls with three types of orofacial clefts--cleft lip, unilateral or bilateral cleft lip and palate and cleft palate. A number of mother that gave the positive answer was relatively high and varied from 24% to 33%. There were no significant differences of the incidence of mother febrile illness between three groups of orofacial clefts in boys and girls. These data support presumption on the harmful effect of febrile illness during early pregnancy on craniofacial development.

Institute of Experimental Medicine Laboratory of Teratology Academy of Sciences of the Czech Republic Prague

Long-term significant seasonal differences in the numbers of new-borns with an orofacial cleft in the Czech Republic - a retrospective study