EFFECTS OF STATIC AND TIME-VARYING (50-HZ) MAGNETIC-FIELDS ON REPRODUCTION AND FETAL DEVELOPMENT IN RATS

Mated Wistar rats were chronically exposed to a static magnetic field (MF) from day 1 to day 20 of pregnancy. Flux density of the MF was 30 mTesla (mT), i.e., within the range of exposures of operators of magnetic resonance imaging (MRI) devices. For comparison with effects of this static field, a time-varying (50-Hz) MF of the same flux density was used. In both experiments, i.e., static or 50-Hz MF exposure, sham-exposed groups of dams served as controls. On day 20, the dams were sacrificed for reproductive and terotological assessment. The litters were evaluated for numbers of implantations, fetal deaths and resorptions, gross external, visceral, and skeletal malformations, and fetal weights. No adverse effects were seen in the darns during MF exposure. The mean number of living fetuses per litter was significantly decreased in the group with static MF exposure, but not the group with 50-Hz MF exposure. Further differences between the two types of field exposure were observed with respect io minor (skeletal) fetal anomalies which were increased in the 50-Hz but not the static MF group. No serious malformations were seen in any group. In both MF-exposed groups, increased skeletal ossification was found, possibly indicating an accelerated prenatal development. In a second experiment with static MF (30 mT) in which darns were exposed for the whole period of pregnancy, and postnatal growth and development of offspring were studied, the postnatal growth was significantly enhanced in offspring following their prenatal MF exposure. In the offspring of this experiment, no behavioral disturbances were determined by several standardized test procedures of behavioral teratology, indicating normal development of brain functions. In summary, the data of the present study indicate that the effects of static and alternating MF on reproduction and fetal development differ: The increased fetal loss during static MF exposure suggests that static MF of such high flux density may induce embryotoxic effects, while 5O-Hz MF exposure does not seem to be associated with any severe reproductive risks. (C) 1994 Wiley-Liss, Inc.