Clinical information and information about the potential hazards in the work and work environment of the pregnant worker are presented that are currently accepted and used by experts. The guidelines were prepared and published to help the practicing obstetrician assemble and interpret the facts necessary for appropriate recommendations to pregnant workers. They are limited, for the most part, to matters of health; important social, economic, legal, labor management, and other nonmedical issues are not resolved here. A bibliography of English and foreign articles is included that deals with the influence of the work and home environment on the health of mother and fetus. Significant gaps in present knowledge of this subject are identified, with emphasis on areas in which study and research are most urgently needed.