Oral clefts and organic solvent exposure during pregnancy.

A cumulative case-referent study concerning selected exposures during pregnancy among mothers to children born with oral clefts has been in progress in Finland since December 1, 1977. The present study covering the initial 3.5 years' material can be regarded as a specific, more detailed extension of earlier retrospective studies concerning environmental factors in the causation of oral clefts, using material accumulated from the Finnish Register of Congenital Malformations. Information on exposures was gained by personal interviews with all the mothers. The analysis of different exposures and the classification of the material were performed blindly. Significantly more case-mothers than referent-mothers had been exposed to organic solvents during the first trimester of pregnancy (P less than 0.05).